From d58d22104b8cc0dc435caaf8da003aa4ee28feed Mon Sep 17 00:00:00 2001
From: kylekatarnls <kylekatarnls@gmail.com>
Date: Tue, 19 Mar 2024 15:49:00 +0100
Subject: [PATCH 1/5] Deprecate Real diff in favor of UTC diff

---
 src/Carbon/CarbonInterface.php   | 18 +++++++----
 src/Carbon/CarbonInterval.php    |  2 +-
 src/Carbon/Traits/Date.php       | 25 +++++++++++++--
 src/Carbon/Traits/Difference.php | 54 ++++++++++++++++++++++----------
 4 files changed, 73 insertions(+), 26 deletions(-)

diff --git a/src/Carbon/CarbonInterface.php b/src/Carbon/CarbonInterface.php
index d44b7c4574..f24311c463 100644
--- a/src/Carbon/CarbonInterface.php
+++ b/src/Carbon/CarbonInterface.php
@@ -1626,10 +1626,11 @@ public function diffForHumans($other = null, $syntax = null, $short = false, $pa
      *
      * @param \Carbon\CarbonInterface|\DateTimeInterface|string|null $date
      * @param bool                                                   $absolute Get the absolute of the difference
+     * @param bool                                                   $utc      Always convert dates to UTC before comparing (if not set, it will do it only if timezones are different)
      *
      * @return float
      */
-    public function diffInDays($date = null, bool $absolute = false): float;
+    public function diffInDays($date = null, bool $absolute = false, bool $utc = false): float;
 
     /**
      * Get the difference in days using a filter closure rounded down.
@@ -1698,20 +1699,22 @@ public function diffInMinutes($date = null, bool $absolute = false): float;
      *
      * @param \Carbon\CarbonInterface|\DateTimeInterface|string|null $date
      * @param bool                                                   $absolute Get the absolute of the difference
+     * @param bool                                                   $utc      Always convert dates to UTC before comparing (if not set, it will do it only if timezones are different)
      *
      * @return float
      */
-    public function diffInMonths($date = null, bool $absolute = false): float;
+    public function diffInMonths($date = null, bool $absolute = false, bool $utc = false): float;
 
     /**
      * Get the difference in quarters rounded down.
      *
      * @param \Carbon\CarbonInterface|\DateTimeInterface|string|null $date
      * @param bool                                                   $absolute Get the absolute of the difference
+     * @param bool                                                   $utc      Always convert dates to UTC before comparing (if not set, it will do it only if timezones are different)
      *
      * @return float
      */
-    public function diffInQuarters($date = null, bool $absolute = false): float;
+    public function diffInQuarters($date = null, bool $absolute = false, bool $utc = false): float;
 
     /**
      * Get the difference in seconds rounded down.
@@ -1729,10 +1732,11 @@ public function diffInSeconds($date = null, bool $absolute = false): float;
      *                                                                         century, millennium
      * @param \Carbon\CarbonInterface|\DateTimeInterface|string|null $date
      * @param bool                                                   $absolute Get the absolute of the difference
+     * @param bool                                                   $utc      Always convert dates to UTC before comparing (if not set, it will do it only if timezones are different)
      *
      * @return float
      */
-    public function diffInUnit(Unit|string $unit, $date = null, bool $absolute = false): float;
+    public function diffInUnit(Unit|string $unit, $date = null, bool $absolute = false, bool $utc = false): float;
 
     /**
      * Get the difference in weekdays rounded down.
@@ -1759,20 +1763,22 @@ public function diffInWeekendDays($date = null, bool $absolute = false): int;
      *
      * @param \Carbon\CarbonInterface|\DateTimeInterface|string|null $date
      * @param bool                                                   $absolute Get the absolute of the difference
+     * @param bool                                                   $utc      Always convert dates to UTC before comparing (if not set, it will do it only if timezones are different)
      *
      * @return float
      */
-    public function diffInWeeks($date = null, bool $absolute = false): float;
+    public function diffInWeeks($date = null, bool $absolute = false, bool $utc = false): float;
 
     /**
      * Get the difference in years
      *
      * @param \Carbon\CarbonInterface|\DateTimeInterface|string|null $date
      * @param bool                                                   $absolute Get the absolute of the difference
+     * @param bool                                                   $utc      Always convert dates to UTC before comparing (if not set, it will do it only if timezones are different)
      *
      * @return float
      */
-    public function diffInYears($date = null, bool $absolute = false): float;
+    public function diffInYears($date = null, bool $absolute = false, bool $utc = false): float;
 
     /**
      * @deprecated To avoid conflict between different third-party libraries, static setters should not be used.
diff --git a/src/Carbon/CarbonInterval.php b/src/Carbon/CarbonInterval.php
index ef01f88afe..aab960eb3c 100644
--- a/src/Carbon/CarbonInterval.php
+++ b/src/Carbon/CarbonInterval.php
@@ -3196,7 +3196,7 @@ private function checkIntegerValue(string $name, mixed $value): void
                 "From 3.0.0, decimal part will no longer be truncated and will be cascaded to smaller units.\n".
                 "- To maintain the current behavior, use explicit cast: $name((int) \$value)\n".
                 "- To adopt the new behavior globally, call CarbonInterval::enableFloatSetters()\n",
-                \E_USER_DEPRECATED
+                \E_USER_DEPRECATED,
             );
         }
     }
diff --git a/src/Carbon/Traits/Date.php b/src/Carbon/Traits/Date.php
index 77feb51ac8..5837f6ec73 100644
--- a/src/Carbon/Traits/Date.php
+++ b/src/Carbon/Traits/Date.php
@@ -2592,8 +2592,29 @@ public static function sleep(int|float $seconds): void
      */
     public function __call(string $method, array $parameters): mixed
     {
-        if (preg_match('/^(?:diff|floatDiff)In(?:Real)?(.+)$/', $method, $match)) {
-            $method = 'diffIn'.$match[1];
+        if (preg_match('/^(diff|floatDiff)In(Real|UTC|Utc)?(.+)$/', $method, $match)) {
+            $mode = strtoupper($match[2] ?? '');
+            $betterMethod = $match[1] === 'floatDiff' ? str_replace('floatDiff', 'diff', $method) : null;
+
+            if ($mode === 'REAL') {
+                $mode = 'UTC';
+                $betterMethod = str_replace($match[1], 'UTC', $betterMethod ?? $method);
+            }
+
+            if ($betterMethod) {
+                @trigger_error(
+                    "Use the method $betterMethod instead to make it more explicit about what it does.\n".
+                    'On next major version, "float" prefix will be removed (as all diff are now returning floating numbers)'.
+                    ' and "Real" methods will be removed in favor of "UTC" because what it actually does is to convert both'.
+                    ' dates to UTC timezone before comparison, while by default it does it only if both dates don\'t have'.
+                    ' exactly the same timezone (Note: 2 timezones with the same offset but different names are considered'.
+                    ' different as it\'s not safe to assume they will always have the same offset).',
+                    \E_USER_DEPRECATED,
+                );
+            }
+
+            $method = 'diffIn'.$match[3];
+            $parameters['utc'] = ($mode === 'UTC');
 
             if (method_exists($this, $method)) {
                 return $this->$method(...$parameters);
diff --git a/src/Carbon/Traits/Difference.php b/src/Carbon/Traits/Difference.php
index d29c81da4d..14e8aeaa79 100644
--- a/src/Carbon/Traits/Difference.php
+++ b/src/Carbon/Traits/Difference.php
@@ -99,10 +99,11 @@ public function diff($date = null, bool $absolute = false, array $skip = []): Ca
      *                                                                         century, millennium
      * @param \Carbon\CarbonInterface|\DateTimeInterface|string|null $date
      * @param bool                                                   $absolute Get the absolute of the difference
+     * @param bool                                                   $utc      Always convert dates to UTC before comparing (if not set, it will do it only if timezones are different)
      *
      * @return float
      */
-    public function diffInUnit(Unit|string $unit, $date = null, bool $absolute = false): float
+    public function diffInUnit(Unit|string $unit, $date = null, bool $absolute = false, bool $utc = false): float
     {
         $unit = static::pluralUnit($unit instanceof Unit ? $unit->value : rtrim($unit, 'z'));
         $method = 'diffIn'.$unit;
@@ -111,7 +112,7 @@ public function diffInUnit(Unit|string $unit, $date = null, bool $absolute = fal
             throw new UnknownUnitException($unit);
         }
 
-        return $this->$method($date, $absolute);
+        return $this->$method($date, $absolute, $utc);
     }
 
     /**
@@ -119,18 +120,27 @@ public function diffInUnit(Unit|string $unit, $date = null, bool $absolute = fal
      *
      * @param \Carbon\CarbonInterface|\DateTimeInterface|string|null $date
      * @param bool                                                   $absolute Get the absolute of the difference
+     * @param bool                                                   $utc      Always convert dates to UTC before comparing (if not set, it will do it only if timezones are different)
      *
      * @return float
      */
-    public function diffInYears($date = null, bool $absolute = false): float
+    public function diffInYears($date = null, bool $absolute = false, bool $utc = false): float
     {
         $start = $this;
         $end = $this->resolveCarbon($date);
+
+        if ($utc) {
+            $start = $start->avoidMutation()->utc();
+            $end = $end->avoidMutation()->utc();
+        }
+
         $ascending = ($start <= $end);
         $sign = $absolute || $ascending ? 1 : -1;
+
         if (!$ascending) {
             [$start, $end] = [$end, $start];
         }
+
         $yearsDiff = (int) $start->diff($end, $absolute)->format('%r%y');
         /** @var Carbon|CarbonImmutable $floorEnd */
         $floorEnd = $start->copy()->addYears($yearsDiff);
@@ -154,12 +164,13 @@ public function diffInYears($date = null, bool $absolute = false): float
      *
      * @param \Carbon\CarbonInterface|\DateTimeInterface|string|null $date
      * @param bool                                                   $absolute Get the absolute of the difference
+     * @param bool                                                   $utc      Always convert dates to UTC before comparing (if not set, it will do it only if timezones are different)
      *
      * @return float
      */
-    public function diffInQuarters($date = null, bool $absolute = false): float
+    public function diffInQuarters($date = null, bool $absolute = false, bool $utc = false): float
     {
-        return $this->diffInMonths($date, $absolute) / static::MONTHS_PER_QUARTER;
+        return $this->diffInMonths($date, $absolute, $utc) / static::MONTHS_PER_QUARTER;
     }
 
     /**
@@ -167,13 +178,20 @@ public function diffInQuarters($date = null, bool $absolute = false): float
      *
      * @param \Carbon\CarbonInterface|\DateTimeInterface|string|null $date
      * @param bool                                                   $absolute Get the absolute of the difference
+     * @param bool                                                   $utc      Always convert dates to UTC before comparing (if not set, it will do it only if timezones are different)
      *
      * @return float
      */
-    public function diffInMonths($date = null, bool $absolute = false): float
+    public function diffInMonths($date = null, bool $absolute = false, bool $utc = false): float
     {
         $start = $this;
-        $end = $this->resolveCarbon($date)->avoidMutation()->setTimezone($this->tz);
+        $end = $this->resolveCarbon($date);
+        $compareUsingUtc = $utc || ($end->timezoneName !== $start->timezoneName);
+
+        if ($compareUsingUtc) {
+            $start = $start->avoidMutation()->utc();
+            $end = $end->avoidMutation()->utc();
+        }
 
         [$yearStart, $monthStart, $dayStart] = explode('-', $start->format('Y-m-dHisu'));
         [$yearEnd, $monthEnd, $dayEnd] = explode('-', $end->format('Y-m-dHisu'));
@@ -196,14 +214,14 @@ public function diffInMonths($date = null, bool $absolute = false): float
         }
 
         /** @var Carbon|CarbonImmutable $floorEnd */
-        $floorEnd = $start->copy()->addMonths($monthsDiff);
+        $floorEnd = $start->avoidMutation()->addMonths($monthsDiff);
 
         if ($floorEnd >= $end) {
             return $sign * $monthsDiff;
         }
 
         /** @var Carbon|CarbonImmutable $startOfMonthAfterFloorEnd */
-        $startOfMonthAfterFloorEnd = $floorEnd->copy()->addMonthNoOverflow()->startOfMonth();
+        $startOfMonthAfterFloorEnd = $floorEnd->avoidMutation()->addMonthNoOverflow()->startOfMonth();
 
         if ($startOfMonthAfterFloorEnd > $end) {
             return $sign * ($monthsDiff + $floorEnd->diffInDays($end) / $floorEnd->daysInMonth);
@@ -217,12 +235,13 @@ public function diffInMonths($date = null, bool $absolute = false): float
      *
      * @param \Carbon\CarbonInterface|\DateTimeInterface|string|null $date
      * @param bool                                                   $absolute Get the absolute of the difference
+     * @param bool                                                   $utc      Always convert dates to UTC before comparing (if not set, it will do it only if timezones are different)
      *
      * @return float
      */
-    public function diffInWeeks($date = null, bool $absolute = false): float
+    public function diffInWeeks($date = null, bool $absolute = false, bool $utc = false): float
     {
-        return $this->diffInDays($date, $absolute) / static::DAYS_PER_WEEK;
+        return $this->diffInDays($date, $absolute, $utc) / static::DAYS_PER_WEEK;
     }
 
     /**
@@ -230,23 +249,24 @@ public function diffInWeeks($date = null, bool $absolute = false): float
      *
      * @param \Carbon\CarbonInterface|\DateTimeInterface|string|null $date
      * @param bool                                                   $absolute Get the absolute of the difference
+     * @param bool                                                   $utc      Always convert dates to UTC before comparing (if not set, it will do it only if timezones are different)
      *
      * @return float
      */
-    public function diffInDays($date = null, bool $absolute = false): float
+    public function diffInDays($date = null, bool $absolute = false, bool $utc = false): float
     {
         $date = $this->resolveCarbon($date);
         $current = $this;
-        $sameTimezone = ($date->timezoneName === $current->timezoneName);
+        $compareUsingUtc = $utc || ($date->timezoneName !== $current->timezoneName);
 
-        if (!$sameTimezone) {
-            $date = $date->copy()->utc();
-            $current = $current->copy()->utc();
+        if ($compareUsingUtc) {
+            $date = $date->avoidMutation()->utc();
+            $current = $current->avoidMutation()->utc();
         }
 
         $interval = $current->diffAsDateInterval($date, $absolute);
 
-        if ($sameTimezone) {
+        if (!$compareUsingUtc) {
             $minutes = $interval->i + ($interval->s + $interval->f) / static::SECONDS_PER_MINUTE;
             $hours = $interval->h + $minutes / static::MINUTES_PER_HOUR;
 

From 7815557422888da8dd8564f6c6934765b2eb5428 Mon Sep 17 00:00:00 2001
From: kylekatarnls <kylekatarnls@gmail.com>
Date: Sun, 24 Mar 2024 18:49:07 +0100
Subject: [PATCH 2/5] Add utc parameters only for methods needing it (units
 bigger than hour)

---
 src/Carbon/Traits/Date.php           |   8 +-
 tests/Carbon/DiffTest.php            |  93 ++++++++++++++++++++---
 tests/CarbonImmutable/DiffTest.php   | 108 ++++++++++++++++++++++++---
 tests/Jenssegers/TranslationTest.php |   1 -
 4 files changed, 185 insertions(+), 25 deletions(-)

diff --git a/src/Carbon/Traits/Date.php b/src/Carbon/Traits/Date.php
index 5837f6ec73..6738ace519 100644
--- a/src/Carbon/Traits/Date.php
+++ b/src/Carbon/Traits/Date.php
@@ -2613,8 +2613,12 @@ public function __call(string $method, array $parameters): mixed
                 );
             }
 
-            $method = 'diffIn'.$match[3];
-            $parameters['utc'] = ($mode === 'UTC');
+            $unit = self::pluralUnit($match[3]);
+            $method = 'diffIn'.ucfirst($unit);
+
+            if (\in_array($unit, ['days', 'weeks', 'months', 'quarters', 'years'])) {
+                $parameters['utc'] = ($mode === 'UTC');
+            }
 
             if (method_exists($this, $method)) {
                 return $this->$method(...$parameters);
diff --git a/tests/Carbon/DiffTest.php b/tests/Carbon/DiffTest.php
index b4929b3a25..00d49b760a 100644
--- a/tests/Carbon/DiffTest.php
+++ b/tests/Carbon/DiffTest.php
@@ -136,9 +136,11 @@ public function testDiffInMonthsWithTimezone()
 
         $this->assertSame(-1, (int) $first->diffInMonths($second, false));
         $this->assertSame(1, (int) $second->diffInMonths($first, false));
-        $this->assertVeryClose(-(1 + 6 / 24 / 31 + 1 / 24 / 28), $first->diffInMonths($second));
+        $this->assertSame($first->utc()->diffInMonths($second->utc()), $first->diffInMonths($second));
+        $this->assertSame($second->utc()->diffInMonths($first->utc()), $second->diffInMonths($first));
+        $this->assertVeryClose(-(1 + 1 / 24 / 31 + 6 / 24 / 28), $first->diffInMonths($second));
         // $second date in Toronto is 2021-12-31 18:00, so we have 6 hours in December (a 31 days month), and 1 hour in February (28 days month)
-        $this->assertVeryClose(1 + (7 / 24 / 28), $second->diffInMonths($first));
+        $this->assertVeryClose(1 + 1 / 24 / 31 + 6 / 24 / 28, $second->diffInMonths($first));
         // Considered in Berlin timezone, the 7 extra hours are in February (28 days month)
 
         $first = new Carbon('2022-02-01 01:00 Europe/Berlin');
@@ -146,7 +148,9 @@ public function testDiffInMonthsWithTimezone()
 
         $this->assertSame(0, (int) $first->diffInMonths($second, false));
         $this->assertSame(0, (int) $second->diffInMonths($first, false));
-        $this->assertVeryClose(-(1 - 6 / 24 / 31 + 1 / 24 / 28), $first->diffInMonths($second));
+        $this->assertSame($first->utc()->diffInMonths($second->utc()), $first->diffInMonths($second));
+        $this->assertSame($second->utc()->diffInMonths($first->utc()), $second->diffInMonths($first));
+        $this->assertVeryClose(-(1 - 5 / 24 / 31), $first->diffInMonths($second));
         $this->assertVeryClose(1 - 5 / 24 / 31, $second->diffInMonths($first));
     }
 
@@ -1868,10 +1872,10 @@ public function testFloatDiffWithRealUnits()
         date_default_timezone_set('UTC');
         $this->assertVeryClose(1.0006944444444446, Carbon::parse('2018-12-01 00:00')->floatDiffInRealDays(Carbon::parse('2018-12-02 00:01'), true));
 
-        $this->assertSame(1.0, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInRealDays('2021-03-28 20:00'));
-        $this->assertSame(2.0, Carbon::parse('2021-03-26 20:00 Europe/Warsaw')->floatDiffInRealDays('2021-03-28 20:00'));
-        $this->assertSame(2.0, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInRealDays('2021-03-29 20:00'));
-        $this->assertSame(1.0, Carbon::parse('2021-10-30 20:00 Europe/Warsaw')->floatDiffInRealDays('2021-10-31 20:00'));
+        $this->assertVeryClose(0.9583333333333334, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInRealDays('2021-03-28 20:00'));
+        $this->assertVeryClose(1.9583333333333335, Carbon::parse('2021-03-26 20:00 Europe/Warsaw')->floatDiffInRealDays('2021-03-28 20:00'));
+        $this->assertVeryClose(1.9583333333333335, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInRealDays('2021-03-29 20:00'));
+        $this->assertVeryClose(1.0416666666666667, Carbon::parse('2021-10-30 20:00 Europe/Warsaw')->floatDiffInRealDays('2021-10-31 20:00'));
         $this->assertVeryClose(1.0006944444444443, Carbon::parse('2018-12-01 00:00')->floatDiffInRealDays(Carbon::parse('2018-12-02 00:01')));
 
         $this->assertVeryClose(1.0006944444444443, Carbon::parse('2018-12-01 00:00')->floatDiffInRealDays(Carbon::parse('2018-12-02 00:01')));
@@ -1909,16 +1913,81 @@ public function testFloatDiffWithRealUnits()
         $this->assertVeryClose(5.325284965308378, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInRealYears(Carbon::parse('2023-06-12 14:24:58.987421')));
         $this->assertVeryClose(-5.325284965308378, Carbon::parse('2023-06-12 14:24:58.987421')->floatDiffInRealYears(Carbon::parse('2018-02-13 20:55:12.321456')));
 
-        $this->assertSame(1.0, Carbon::parse('2018-10-01 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-11-01 00:00:00', 'Europe/Paris'), true));
+        $this->assertVeryClose(1.0336021505376345, Carbon::parse('2018-10-01 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-11-01 00:00:00', 'Europe/Paris'), true));
         $this->assertSame(1.0, Carbon::parse('2018-10-28 00:00:00')->floatDiffInRealMonths(Carbon::parse('2018-11-28 00:00:00'), true));
-        $this->assertSame(1.0, Carbon::parse('2018-10-28 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-11-28 00:00:00', 'Europe/Paris'), true));
+        $this->assertVeryClose(1.0013888888888889, Carbon::parse('2018-10-28 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-11-28 00:00:00', 'Europe/Paris'), true));
 
-        $this->assertSame(-1.0, Carbon::parse('2018-11-01 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-10-01 00:00:00', 'Europe/Paris')));
+        $this->assertVeryClose(-1.0336021505376345, Carbon::parse('2018-11-01 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-10-01 00:00:00', 'Europe/Paris')));
         $this->assertSame(-1.0, Carbon::parse('2018-11-28 00:00:00')->floatDiffInRealMonths(Carbon::parse('2018-10-28 00:00:00')));
-        $this->assertSame(-1.0, Carbon::parse('2018-11-28 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-10-28 00:00:00', 'Europe/Paris')));
+        $this->assertVeryClose(-1.0013888888888889, Carbon::parse('2018-11-28 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-10-28 00:00:00', 'Europe/Paris')));
 
         Carbon::setTestNow('2021-03-28 20:00 Europe/Warsaw');
-        $this->assertSame(1.0, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInRealDays());
+        $this->assertSame(0.9583333333333334, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInRealDays());
+    }
+
+    public function testFloatDiffWithUTCUnits()
+    {
+        $from = Carbon::parse('2021-03-27 20:00 Europe/Warsaw');
+        $to = Carbon::parse('2021-03-27 20:00 Europe/London');
+        $from->floatDiffInUtcDays($to);
+
+        $this->assertSame('2021-03-27 20:00:00 Europe/Warsaw', $from->format('Y-m-d H:i:s e'));
+        $this->assertSame('2021-03-27 20:00:00 Europe/London', $to->format('Y-m-d H:i:s e'));
+
+        date_default_timezone_set('UTC');
+        $this->assertVeryClose(1.0006944444444446, Carbon::parse('2018-12-01 00:00')->floatDiffInUtcDays(Carbon::parse('2018-12-02 00:01'), true));
+
+        $this->assertVeryClose(0.9583333333333334, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInUtcDays('2021-03-28 20:00'));
+        $this->assertVeryClose(1.9583333333333335, Carbon::parse('2021-03-26 20:00 Europe/Warsaw')->floatDiffInUtcDays('2021-03-28 20:00'));
+        $this->assertVeryClose(1.9583333333333335, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInUtcDays('2021-03-29 20:00'));
+        $this->assertVeryClose(1.0416666666666667, Carbon::parse('2021-10-30 20:00 Europe/Warsaw')->floatDiffInUtcDays('2021-10-31 20:00'));
+        $this->assertVeryClose(1.0006944444444443, Carbon::parse('2018-12-01 00:00')->floatDiffInUtcDays(Carbon::parse('2018-12-02 00:01')));
+
+        $this->assertVeryClose(1.0006944444444443, Carbon::parse('2018-12-01 00:00')->floatDiffInUtcDays(Carbon::parse('2018-12-02 00:01')));
+        $this->assertVeryClose(1.0006944444444443 / 7, Carbon::parse('2018-12-01 00:00')->floatDiffInUtcWeeks(Carbon::parse('2018-12-02 00:01')));
+
+        $this->assertVeryClose(0.9714742503779745, Carbon::parse('2018-03-13 20:55:12.321456')->floatDiffInUtcMonths(Carbon::parse('2018-04-12 14:24:58.987421'), true));
+        $this->assertVeryClose(0.9714742503779745, Carbon::parse('2018-04-12 14:24:58.987421')->floatDiffInUtcMonths(Carbon::parse('2018-03-13 20:55:12.321456'), true));
+        $this->assertVeryClose(0.9714742503779745, Carbon::parse('2018-03-13 20:55:12.321456')->floatDiffInUtcMonths(Carbon::parse('2018-04-12 14:24:58.987421'), false));
+        $this->assertVeryClose(-0.9714742503779745, Carbon::parse('2018-04-12 14:24:58.987421')->floatDiffInUtcMonths(Carbon::parse('2018-03-13 20:55:12.321456'), false));
+
+        $this->assertVeryClose(1.0006944444444443 / 7, Carbon::parse('2018-12-01 00:00')->floatDiffInUtcWeeks(Carbon::parse('2018-12-02 00:01')));
+        $this->assertVeryClose(1.0006944444444443 / 7, Carbon::parse('2018-12-01 00:00')->floatDiffInUtcWeeks(Carbon::parse('2018-12-02 00:01'), true));
+
+        $this->assertVeryClose(0.9714742503779745, Carbon::parse('2018-03-13 20:55:12.321456')->floatDiffInUtcMonths(Carbon::parse('2018-04-12 14:24:58.987421')));
+        $this->assertVeryClose(-0.9714742503779745, Carbon::parse('2018-04-12 14:24:58.987421')->floatDiffInUtcMonths(Carbon::parse('2018-03-13 20:55:12.321456')));
+
+        $this->assertVeryClose(16.557633744585264, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcMonths(Carbon::parse('2019-06-30 14:24:58.987421'), true));
+
+        $this->assertVeryClose(15.971474250377973, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcMonths(Carbon::parse('2019-06-12 14:24:58.987421'), true));
+        $this->assertVeryClose(15.971474250377973, Carbon::parse('2019-06-12 14:24:58.987421')->floatDiffInUtcMonths(Carbon::parse('2018-02-13 20:55:12.321456'), true));
+        $this->assertVeryClose(15.971474250377973, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcMonths(Carbon::parse('2019-06-12 14:24:58.987421')));
+        $this->assertVeryClose(-15.971474250377973, Carbon::parse('2019-06-12 14:24:58.987421')->floatDiffInUtcMonths(Carbon::parse('2018-02-13 20:55:12.321456')));
+
+        $this->assertSame(1.0, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2019-02-13 20:55:12.321456'), true));
+        $this->assertVeryClose(1.3746000338015283, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2019-06-30 14:24:58.987421'), true));
+        $this->assertVeryClose(0.9609014036645421, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2019-01-30 14:24:58.987421'), true));
+
+        $this->assertVeryClose(1.3252849653083778, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2019-06-12 14:24:58.987421'), true));
+        $this->assertVeryClose(1.3252849653083778, Carbon::parse('2019-06-12 14:24:58.987421')->floatDiffInUtcYears(Carbon::parse('2018-02-13 20:55:12.321456'), true));
+        $this->assertVeryClose(1.3252849653083778, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2019-06-12 14:24:58.987421')));
+        $this->assertVeryClose(-1.3252849653083778, Carbon::parse('2019-06-12 14:24:58.987421')->floatDiffInUtcYears(Carbon::parse('2018-02-13 20:55:12.321456')));
+
+        $this->assertVeryClose(5.325284965308378, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2023-06-12 14:24:58.987421'), true));
+        $this->assertVeryClose(5.325284965308378, Carbon::parse('2023-06-12 14:24:58.987421')->floatDiffInUtcYears(Carbon::parse('2018-02-13 20:55:12.321456'), true));
+        $this->assertVeryClose(5.325284965308378, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2023-06-12 14:24:58.987421')));
+        $this->assertVeryClose(-5.325284965308378, Carbon::parse('2023-06-12 14:24:58.987421')->floatDiffInUtcYears(Carbon::parse('2018-02-13 20:55:12.321456')));
+
+        $this->assertVeryClose(1.0336021505376345, Carbon::parse('2018-10-01 00:00:00', 'Europe/Paris')->floatDiffInUtcMonths(Carbon::parse('2018-11-01 00:00:00', 'Europe/Paris'), true));
+        $this->assertSame(1.0, Carbon::parse('2018-10-28 00:00:00')->floatDiffInUtcMonths(Carbon::parse('2018-11-28 00:00:00'), true));
+        $this->assertVeryClose(1.0013888888888889, Carbon::parse('2018-10-28 00:00:00', 'Europe/Paris')->floatDiffInUtcMonths(Carbon::parse('2018-11-28 00:00:00', 'Europe/Paris'), true));
+
+        $this->assertVeryClose(-1.0336021505376345, Carbon::parse('2018-11-01 00:00:00', 'Europe/Paris')->floatDiffInUtcMonths(Carbon::parse('2018-10-01 00:00:00', 'Europe/Paris')));
+        $this->assertSame(-1.0, Carbon::parse('2018-11-28 00:00:00')->floatDiffInUtcMonths(Carbon::parse('2018-10-28 00:00:00')));
+        $this->assertVeryClose(-1.0013888888888889, Carbon::parse('2018-11-28 00:00:00', 'Europe/Paris')->floatDiffInUtcMonths(Carbon::parse('2018-10-28 00:00:00', 'Europe/Paris')));
+
+        Carbon::setTestNow('2021-03-28 20:00 Europe/Warsaw');
+        $this->assertSame(0.9583333333333334, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInUtcDays());
     }
 
     /**
diff --git a/tests/CarbonImmutable/DiffTest.php b/tests/CarbonImmutable/DiffTest.php
index 67c7207bf6..f91aeef9b5 100644
--- a/tests/CarbonImmutable/DiffTest.php
+++ b/tests/CarbonImmutable/DiffTest.php
@@ -1684,15 +1684,35 @@ public function testFloatDiff()
 
     public function testFloatDiffWithRealUnits()
     {
-        date_default_timezone_set('UTC');
+        $from = Carbon::parse('2021-03-27 20:00 Europe/Warsaw');
+        $to = Carbon::parse('2021-03-27 20:00 Europe/London');
+        $from->floatDiffInRealDays($to);
+
+        $this->assertSame('2021-03-27 20:00:00 Europe/Warsaw', $from->format('Y-m-d H:i:s e'));
+        $this->assertSame('2021-03-27 20:00:00 Europe/London', $to->format('Y-m-d H:i:s e'));
 
+        date_default_timezone_set('UTC');
         $this->assertVeryClose(1.0006944444444446, Carbon::parse('2018-12-01 00:00')->floatDiffInRealDays(Carbon::parse('2018-12-02 00:01'), true));
-        $this->assertVeryClose(1.0006944444444446 / 7, Carbon::parse('2018-12-01 00:00')->floatDiffInRealWeeks(Carbon::parse('2018-12-02 00:01'), true));
 
-        $this->assertVeryClose(0.9714742503779743, Carbon::parse('2018-03-13 20:55:12.321456')->floatDiffInRealMonths(Carbon::parse('2018-04-12 14:24:58.987421'), true));
-        $this->assertVeryClose(0.9714742503779743, Carbon::parse('2018-04-12 14:24:58.987421')->floatDiffInRealMonths(Carbon::parse('2018-03-13 20:55:12.321456'), true));
-        $this->assertVeryClose(0.9714742503779743, Carbon::parse('2018-03-13 20:55:12.321456')->floatDiffInRealMonths(Carbon::parse('2018-04-12 14:24:58.987421')));
-        $this->assertVeryClose(-0.9714742503779743, Carbon::parse('2018-04-12 14:24:58.987421')->floatDiffInRealMonths(Carbon::parse('2018-03-13 20:55:12.321456')));
+        $this->assertVeryClose(0.9583333333333334, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInRealDays('2021-03-28 20:00'));
+        $this->assertVeryClose(1.9583333333333335, Carbon::parse('2021-03-26 20:00 Europe/Warsaw')->floatDiffInRealDays('2021-03-28 20:00'));
+        $this->assertVeryClose(1.9583333333333335, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInRealDays('2021-03-29 20:00'));
+        $this->assertVeryClose(1.0416666666666667, Carbon::parse('2021-10-30 20:00 Europe/Warsaw')->floatDiffInRealDays('2021-10-31 20:00'));
+        $this->assertVeryClose(1.0006944444444443, Carbon::parse('2018-12-01 00:00')->floatDiffInRealDays(Carbon::parse('2018-12-02 00:01')));
+
+        $this->assertVeryClose(1.0006944444444443, Carbon::parse('2018-12-01 00:00')->floatDiffInRealDays(Carbon::parse('2018-12-02 00:01')));
+        $this->assertVeryClose(1.0006944444444443 / 7, Carbon::parse('2018-12-01 00:00')->floatDiffInRealWeeks(Carbon::parse('2018-12-02 00:01')));
+
+        $this->assertVeryClose(0.9714742503779745, Carbon::parse('2018-03-13 20:55:12.321456')->floatDiffInRealMonths(Carbon::parse('2018-04-12 14:24:58.987421'), true));
+        $this->assertVeryClose(0.9714742503779745, Carbon::parse('2018-04-12 14:24:58.987421')->floatDiffInRealMonths(Carbon::parse('2018-03-13 20:55:12.321456'), true));
+        $this->assertVeryClose(0.9714742503779745, Carbon::parse('2018-03-13 20:55:12.321456')->floatDiffInRealMonths(Carbon::parse('2018-04-12 14:24:58.987421'), false));
+        $this->assertVeryClose(-0.9714742503779745, Carbon::parse('2018-04-12 14:24:58.987421')->floatDiffInRealMonths(Carbon::parse('2018-03-13 20:55:12.321456'), false));
+
+        $this->assertVeryClose(1.0006944444444443 / 7, Carbon::parse('2018-12-01 00:00')->floatDiffInRealWeeks(Carbon::parse('2018-12-02 00:01')));
+        $this->assertVeryClose(1.0006944444444443 / 7, Carbon::parse('2018-12-01 00:00')->floatDiffInRealWeeks(Carbon::parse('2018-12-02 00:01'), true));
+
+        $this->assertVeryClose(0.9714742503779745, Carbon::parse('2018-03-13 20:55:12.321456')->floatDiffInRealMonths(Carbon::parse('2018-04-12 14:24:58.987421')));
+        $this->assertVeryClose(-0.9714742503779745, Carbon::parse('2018-04-12 14:24:58.987421')->floatDiffInRealMonths(Carbon::parse('2018-03-13 20:55:12.321456')));
 
         $this->assertVeryClose(16.557633744585264, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInRealMonths(Carbon::parse('2019-06-30 14:24:58.987421'), true));
 
@@ -1715,13 +1735,81 @@ public function testFloatDiffWithRealUnits()
         $this->assertVeryClose(5.325284965308378, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInRealYears(Carbon::parse('2023-06-12 14:24:58.987421')));
         $this->assertVeryClose(-5.325284965308378, Carbon::parse('2023-06-12 14:24:58.987421')->floatDiffInRealYears(Carbon::parse('2018-02-13 20:55:12.321456')));
 
-        $this->assertSame(1.0, Carbon::parse('2018-10-01 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-11-01 00:00:00', 'Europe/Paris'), true));
+        $this->assertVeryClose(1.0336021505376345, Carbon::parse('2018-10-01 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-11-01 00:00:00', 'Europe/Paris'), true));
         $this->assertSame(1.0, Carbon::parse('2018-10-28 00:00:00')->floatDiffInRealMonths(Carbon::parse('2018-11-28 00:00:00'), true));
-        $this->assertSame(1.0, Carbon::parse('2018-10-28 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-11-28 00:00:00', 'Europe/Paris'), true));
+        $this->assertVeryClose(1.0013888888888889, Carbon::parse('2018-10-28 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-11-28 00:00:00', 'Europe/Paris'), true));
 
-        $this->assertSame(-1.0, Carbon::parse('2018-11-01 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-10-01 00:00:00', 'Europe/Paris')));
+        $this->assertVeryClose(-1.0336021505376345, Carbon::parse('2018-11-01 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-10-01 00:00:00', 'Europe/Paris')));
         $this->assertSame(-1.0, Carbon::parse('2018-11-28 00:00:00')->floatDiffInRealMonths(Carbon::parse('2018-10-28 00:00:00')));
-        $this->assertSame(-1.0, Carbon::parse('2018-11-28 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-10-28 00:00:00', 'Europe/Paris')));
+        $this->assertVeryClose(-1.0013888888888889, Carbon::parse('2018-11-28 00:00:00', 'Europe/Paris')->floatDiffInRealMonths(Carbon::parse('2018-10-28 00:00:00', 'Europe/Paris')));
+
+        Carbon::setTestNow('2021-03-28 20:00 Europe/Warsaw');
+        $this->assertSame(0.9583333333333334, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInRealDays());
+    }
+
+    public function testFloatDiffWithUTCUnits()
+    {
+        $from = Carbon::parse('2021-03-27 20:00 Europe/Warsaw');
+        $to = Carbon::parse('2021-03-27 20:00 Europe/London');
+        $from->floatDiffInUtcDays($to);
+
+        $this->assertSame('2021-03-27 20:00:00 Europe/Warsaw', $from->format('Y-m-d H:i:s e'));
+        $this->assertSame('2021-03-27 20:00:00 Europe/London', $to->format('Y-m-d H:i:s e'));
+
+        date_default_timezone_set('UTC');
+        $this->assertVeryClose(1.0006944444444446, Carbon::parse('2018-12-01 00:00')->floatDiffInUtcDays(Carbon::parse('2018-12-02 00:01'), true));
+
+        $this->assertVeryClose(0.9583333333333334, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInUtcDays('2021-03-28 20:00'));
+        $this->assertVeryClose(1.9583333333333335, Carbon::parse('2021-03-26 20:00 Europe/Warsaw')->floatDiffInUtcDays('2021-03-28 20:00'));
+        $this->assertVeryClose(1.9583333333333335, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInUtcDays('2021-03-29 20:00'));
+        $this->assertVeryClose(1.0416666666666667, Carbon::parse('2021-10-30 20:00 Europe/Warsaw')->floatDiffInUtcDays('2021-10-31 20:00'));
+        $this->assertVeryClose(1.0006944444444443, Carbon::parse('2018-12-01 00:00')->floatDiffInUtcDays(Carbon::parse('2018-12-02 00:01')));
+
+        $this->assertVeryClose(1.0006944444444443, Carbon::parse('2018-12-01 00:00')->floatDiffInUtcDays(Carbon::parse('2018-12-02 00:01')));
+        $this->assertVeryClose(1.0006944444444443 / 7, Carbon::parse('2018-12-01 00:00')->floatDiffInUtcWeeks(Carbon::parse('2018-12-02 00:01')));
+
+        $this->assertVeryClose(0.9714742503779745, Carbon::parse('2018-03-13 20:55:12.321456')->floatDiffInUtcMonths(Carbon::parse('2018-04-12 14:24:58.987421'), true));
+        $this->assertVeryClose(0.9714742503779745, Carbon::parse('2018-04-12 14:24:58.987421')->floatDiffInUtcMonths(Carbon::parse('2018-03-13 20:55:12.321456'), true));
+        $this->assertVeryClose(0.9714742503779745, Carbon::parse('2018-03-13 20:55:12.321456')->floatDiffInUtcMonths(Carbon::parse('2018-04-12 14:24:58.987421'), false));
+        $this->assertVeryClose(-0.9714742503779745, Carbon::parse('2018-04-12 14:24:58.987421')->floatDiffInUtcMonths(Carbon::parse('2018-03-13 20:55:12.321456'), false));
+
+        $this->assertVeryClose(1.0006944444444443 / 7, Carbon::parse('2018-12-01 00:00')->floatDiffInUtcWeeks(Carbon::parse('2018-12-02 00:01')));
+        $this->assertVeryClose(1.0006944444444443 / 7, Carbon::parse('2018-12-01 00:00')->floatDiffInUtcWeeks(Carbon::parse('2018-12-02 00:01'), true));
+
+        $this->assertVeryClose(0.9714742503779745, Carbon::parse('2018-03-13 20:55:12.321456')->floatDiffInUtcMonths(Carbon::parse('2018-04-12 14:24:58.987421')));
+        $this->assertVeryClose(-0.9714742503779745, Carbon::parse('2018-04-12 14:24:58.987421')->floatDiffInUtcMonths(Carbon::parse('2018-03-13 20:55:12.321456')));
+
+        $this->assertVeryClose(16.557633744585264, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcMonths(Carbon::parse('2019-06-30 14:24:58.987421'), true));
+
+        $this->assertVeryClose(15.971474250377973, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcMonths(Carbon::parse('2019-06-12 14:24:58.987421'), true));
+        $this->assertVeryClose(15.971474250377973, Carbon::parse('2019-06-12 14:24:58.987421')->floatDiffInUtcMonths(Carbon::parse('2018-02-13 20:55:12.321456'), true));
+        $this->assertVeryClose(15.971474250377973, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcMonths(Carbon::parse('2019-06-12 14:24:58.987421')));
+        $this->assertVeryClose(-15.971474250377973, Carbon::parse('2019-06-12 14:24:58.987421')->floatDiffInUtcMonths(Carbon::parse('2018-02-13 20:55:12.321456')));
+
+        $this->assertSame(1.0, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2019-02-13 20:55:12.321456'), true));
+        $this->assertVeryClose(1.3746000338015283, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2019-06-30 14:24:58.987421'), true));
+        $this->assertVeryClose(0.9609014036645421, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2019-01-30 14:24:58.987421'), true));
+
+        $this->assertVeryClose(1.3252849653083778, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2019-06-12 14:24:58.987421'), true));
+        $this->assertVeryClose(1.3252849653083778, Carbon::parse('2019-06-12 14:24:58.987421')->floatDiffInUtcYears(Carbon::parse('2018-02-13 20:55:12.321456'), true));
+        $this->assertVeryClose(1.3252849653083778, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2019-06-12 14:24:58.987421')));
+        $this->assertVeryClose(-1.3252849653083778, Carbon::parse('2019-06-12 14:24:58.987421')->floatDiffInUtcYears(Carbon::parse('2018-02-13 20:55:12.321456')));
+
+        $this->assertVeryClose(5.325284965308378, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2023-06-12 14:24:58.987421'), true));
+        $this->assertVeryClose(5.325284965308378, Carbon::parse('2023-06-12 14:24:58.987421')->floatDiffInUtcYears(Carbon::parse('2018-02-13 20:55:12.321456'), true));
+        $this->assertVeryClose(5.325284965308378, Carbon::parse('2018-02-13 20:55:12.321456')->floatDiffInUtcYears(Carbon::parse('2023-06-12 14:24:58.987421')));
+        $this->assertVeryClose(-5.325284965308378, Carbon::parse('2023-06-12 14:24:58.987421')->floatDiffInUtcYears(Carbon::parse('2018-02-13 20:55:12.321456')));
+
+        $this->assertVeryClose(1.0336021505376345, Carbon::parse('2018-10-01 00:00:00', 'Europe/Paris')->floatDiffInUtcMonths(Carbon::parse('2018-11-01 00:00:00', 'Europe/Paris'), true));
+        $this->assertSame(1.0, Carbon::parse('2018-10-28 00:00:00')->floatDiffInUtcMonths(Carbon::parse('2018-11-28 00:00:00'), true));
+        $this->assertVeryClose(1.0013888888888889, Carbon::parse('2018-10-28 00:00:00', 'Europe/Paris')->floatDiffInUtcMonths(Carbon::parse('2018-11-28 00:00:00', 'Europe/Paris'), true));
+
+        $this->assertVeryClose(-1.0336021505376345, Carbon::parse('2018-11-01 00:00:00', 'Europe/Paris')->floatDiffInUtcMonths(Carbon::parse('2018-10-01 00:00:00', 'Europe/Paris')));
+        $this->assertSame(-1.0, Carbon::parse('2018-11-28 00:00:00')->floatDiffInUtcMonths(Carbon::parse('2018-10-28 00:00:00')));
+        $this->assertVeryClose(-1.0013888888888889, Carbon::parse('2018-11-28 00:00:00', 'Europe/Paris')->floatDiffInUtcMonths(Carbon::parse('2018-10-28 00:00:00', 'Europe/Paris')));
+
+        Carbon::setTestNow('2021-03-28 20:00 Europe/Warsaw');
+        $this->assertSame(0.9583333333333334, Carbon::parse('2021-03-27 20:00 Europe/Warsaw')->floatDiffInUtcDays());
     }
 
     /**
diff --git a/tests/Jenssegers/TranslationTest.php b/tests/Jenssegers/TranslationTest.php
index 809c650b3d..555bdd1ace 100644
--- a/tests/Jenssegers/TranslationTest.php
+++ b/tests/Jenssegers/TranslationTest.php
@@ -77,7 +77,6 @@ public function testCustomSuffix()
         $this->assertSame('vor 5 Sekunden', $date->ago());
     }
 
-    /** @group i */
     public function testTimespanTranslated()
     {
         JenssegersDate::setLocale('nl');

From d735797a4b4d1a0d4e1e96cbc0897aa769aa70ac Mon Sep 17 00:00:00 2001
From: kylekatarnls <kylekatarnls@gmail.com>
Date: Sun, 24 Mar 2024 19:15:57 +0100
Subject: [PATCH 3/5] Update dependencies

---
 composer.json | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/composer.json b/composer.json
index f71568b397..d4a00ffd85 100644
--- a/composer.json
+++ b/composer.json
@@ -51,14 +51,14 @@
     "require-dev": {
         "doctrine/dbal": "^3.6.3 || ^4.0",
         "doctrine/orm": "^2.15.2 || ^3.0",
-        "friendsofphp/php-cs-fixer": "^3.18.0",
-        "kylekatarnls/multi-tester": "^2.2.0",
-        "ondrejmirtes/better-reflection": "^6.11.0.0",
-        "phpmd/phpmd": "^2.13.0",
-        "phpstan/extension-installer": "^1.3.0",
-        "phpstan/phpstan": "^1.10.20",
-        "phpunit/phpunit": "^10.2.2",
-        "squizlabs/php_codesniffer": "^3.7.2"
+        "friendsofphp/php-cs-fixer": "^3.52.1",
+        "kylekatarnls/multi-tester": "^2.5.3",
+        "ondrejmirtes/better-reflection": "^6.25.0.4",
+        "phpmd/phpmd": "^2.15.0",
+        "phpstan/extension-installer": "^1.3.1",
+        "phpstan/phpstan": "^1.10.65",
+        "phpunit/phpunit": "^10.5.15",
+        "squizlabs/php_codesniffer": "^3.9.0"
     },
     "provide": {
         "psr/clock-implementation": "1.0"

From d504c0852de7d1fc933f20343c4b3308c8ed9d01 Mon Sep 17 00:00:00 2001
From: kylekatarnls <kylekatarnls@gmail.com>
Date: Wed, 27 Mar 2024 13:15:42 +0100
Subject: [PATCH 4/5] Downgrade nikic/php-parser in CI

---
 .github/workflows/tests.yml          | 10 ++--
 phpdoc.php                           | 12 ++---
 src/Carbon/Traits/Units.php          | 68 ++++++++++++++++++++--------
 tests/PHPStan/MacroExtensionTest.php |  2 +-
 4 files changed, 64 insertions(+), 28 deletions(-)

diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 42a4f99acc..6bef6abd52 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -63,11 +63,15 @@ jobs:
 
       - name: Select PHPUnit version
         if: matrix.phpunit
-        run: composer require --no-update phpunit/phpunit:^${{ matrix.phpunit }} --no-interaction --dev
+        run: composer require --no-update --no-interaction --dev "phpunit/phpunit:^${{ matrix.phpunit }}"
 
       - name: Remove conflicting optional dependencies
         if: matrix.phpunit >= 11
-        run: composer remove --no-update ondrejmirtes/better-reflection --no-interaction --dev
+        run: composer remove --no-update --no-interaction --dev ondrejmirtes/better-reflection
+
+      - name: Downgrade nikic/php-parser
+        if: matrix.phpunit < 11
+        run: composer require --no-update --no-interaction --dev "nikic/php-parser:^4"
 
       - name: Install dependencies
         uses: nick-fields/retry@v3
@@ -76,7 +80,7 @@ jobs:
           timeout_minutes: 10
           max_attempts: 3
           command: |
-            composer remove --no-update phpmd/phpmd friendsofphp/php-cs-fixer kylekatarnls/multi-tester --no-interaction --dev;
+            composer remove --no-update --no-interaction --dev phpmd/phpmd friendsofphp/php-cs-fixer kylekatarnls/multi-tester;
             composer update --prefer-dist --no-progress --prefer-${{ matrix.setup || 'stable' }} ${{ matrix.classmap-authoritative && '--classmap-authoritative' || '' }}${{ matrix.php >= 8.2 && ' --ignore-platform-reqs' || '' }};
 
       - name: Run test suite
diff --git a/phpdoc.php b/phpdoc.php
index 18f892909e..1797797211 100644
--- a/phpdoc.php
+++ b/phpdoc.php
@@ -26,7 +26,7 @@
     ['call', 'isSameUnit'],
     ['call', 'setUnit'],
     ['call', 'addUnit'],
-    ['call', 'addRealUnit'],
+    ['call', 'addUTCUnit'],
     ['call', 'roundUnit'],
     ['call', 'diffForHumans'],
 ];
@@ -418,7 +418,7 @@ function dumpParameter(string $method, ReflectionParameter $parameter): string
 
                     break;
 
-                case 'addRealUnit':
+                case 'addUTCUnit':
                     $unit = $vars->name;
                     $unitName = unitName($unit);
                     $plUnit = pluralize($unit);
@@ -426,25 +426,25 @@ function dumpParameter(string $method, ReflectionParameter $parameter): string
                     $autoDocLines[] = [
                         '@method',
                         'self',
-                        'addReal'.ucFirst($plUnit).'(int|float $value = 1)',
+                        'addUTC'.ucFirst($plUnit).'(int|float $value = 1)',
                         "Add $plUnitName (the \$value count passed in) to the instance (using timestamp).",
                     ];
                     $autoDocLines[] = [
                         '@method',
                         'self',
-                        'addReal'.ucFirst($unit).'()',
+                        'addUTC'.ucFirst($unit).'()',
                         "Add one $unitName to the instance (using timestamp).",
                     ];
                     $autoDocLines[] = [
                         '@method',
                         'self',
-                        'subReal'.ucFirst($plUnit).'(int|float $value = 1)',
+                        'subUTC'.ucFirst($plUnit).'(int|float $value = 1)',
                         "Sub $plUnitName (the \$value count passed in) to the instance (using timestamp).",
                     ];
                     $autoDocLines[] = [
                         '@method',
                         'self',
-                        'subReal'.ucFirst($unit).'()',
+                        'subUTC'.ucFirst($unit).'()',
                         "Sub one $unitName to the instance (using timestamp).",
                     ];
                     $autoDocLines[] = [
diff --git a/src/Carbon/Traits/Units.php b/src/Carbon/Traits/Units.php
index d8434dab4e..25c1c4f85a 100644
--- a/src/Carbon/Traits/Units.php
+++ b/src/Carbon/Traits/Units.php
@@ -34,6 +34,8 @@
 trait Units
 {
     /**
+     * @deprecated Prefer to use add addUTCUnit() which more accurately defines what it's doing.
+     *
      * Add seconds to the instance using timestamp. Positive $value travels
      * forward while negative $value travels into the past.
      *
@@ -43,14 +45,28 @@ trait Units
      * @return static
      */
     public function addRealUnit(string $unit, $value = 1): static
+    {
+        return $this->addUTCUnit($unit, $value);
+    }
+
+    /**
+     * Add seconds to the instance using timestamp. Positive $value travels
+     * forward while negative $value travels into the past.
+     *
+     * @param string         $unit
+     * @param int|float|null $value
+     *
+     * @return static
+     */
+    public function addUTCUnit(string $unit, $value = 1): static
     {
         $value ??= 0;
 
         switch ($unit) {
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'micro':
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'microsecond':
                 /* @var CarbonInterface $this */
                 $diff = $this->microsecond + $value;
@@ -63,71 +79,71 @@ public function addRealUnit(string $unit, $value = 1): static
 
                 return $this->tz('UTC')->modify("@$time.$microtime")->setTimezone($timezone);
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'milli':
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'millisecond':
-                return $this->addRealUnit('microsecond', $value * static::MICROSECONDS_PER_MILLISECOND);
+                return $this->addUTCUnit('microsecond', $value * static::MICROSECONDS_PER_MILLISECOND);
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'second':
                 break;
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'minute':
                 $value *= static::SECONDS_PER_MINUTE;
 
                 break;
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'hour':
                 $value *= static::MINUTES_PER_HOUR * static::SECONDS_PER_MINUTE;
 
                 break;
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'day':
                 $value *= static::HOURS_PER_DAY * static::MINUTES_PER_HOUR * static::SECONDS_PER_MINUTE;
 
                 break;
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'week':
                 $value *= static::DAYS_PER_WEEK * static::HOURS_PER_DAY * static::MINUTES_PER_HOUR * static::SECONDS_PER_MINUTE;
 
                 break;
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'month':
                 $value *= 30 * static::HOURS_PER_DAY * static::MINUTES_PER_HOUR * static::SECONDS_PER_MINUTE;
 
                 break;
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'quarter':
                 $value *= static::MONTHS_PER_QUARTER * 30 * static::HOURS_PER_DAY * static::MINUTES_PER_HOUR * static::SECONDS_PER_MINUTE;
 
                 break;
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'year':
                 $value *= 365 * static::HOURS_PER_DAY * static::MINUTES_PER_HOUR * static::SECONDS_PER_MINUTE;
 
                 break;
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'decade':
                 $value *= static::YEARS_PER_DECADE * 365 * static::HOURS_PER_DAY * static::MINUTES_PER_HOUR * static::SECONDS_PER_MINUTE;
 
                 break;
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'century':
                 $value *= static::YEARS_PER_CENTURY * 365 * static::HOURS_PER_DAY * static::MINUTES_PER_HOUR * static::SECONDS_PER_MINUTE;
 
                 break;
 
-            // @call addRealUnit
+            // @call addUTCUnit
             case 'millennium':
                 $value *= static::YEARS_PER_MILLENNIUM * 365 * static::HOURS_PER_DAY * static::MINUTES_PER_HOUR * static::SECONDS_PER_MINUTE;
 
@@ -147,10 +163,12 @@ public function addRealUnit(string $unit, $value = 1): static
         );
         $date = $this->setTimestamp($this->getTimestamp() + $seconds);
 
-        return $microseconds ? $date->addRealUnit('microsecond', $microseconds) : $date;
+        return $microseconds ? $date->addUTCUnit('microsecond', $microseconds) : $date;
     }
 
     /**
+     * @deprecated Prefer to use add subUTCUnit() which more accurately defines what it's doing.
+     *
      * Subtract seconds to the instance using timestamp. Positive $value travels
      * into the past while negative $value travels forward.
      *
@@ -161,7 +179,21 @@ public function addRealUnit(string $unit, $value = 1): static
      */
     public function subRealUnit($unit, $value = 1): static
     {
-        return $this->addRealUnit($unit, -$value);
+        return $this->addUTCUnit($unit, -$value);
+    }
+
+    /**
+     * Subtract seconds to the instance using timestamp. Positive $value travels
+     * into the past while negative $value travels forward.
+     *
+     * @param string $unit
+     * @param int    $value
+     *
+     * @return static
+     */
+    public function subUTCUnit($unit, $value = 1): static
+    {
+        return $this->addUTCUnit($unit, -$value);
     }
 
     /**
diff --git a/tests/PHPStan/MacroExtensionTest.php b/tests/PHPStan/MacroExtensionTest.php
index 3491d1b180..8e4ce719e9 100644
--- a/tests/PHPStan/MacroExtensionTest.php
+++ b/tests/PHPStan/MacroExtensionTest.php
@@ -22,6 +22,7 @@
 use PHPUnit\Framework\Attributes\RequiresPhpunit;
 use Tests\AbstractTestCase;
 
+#[RequiresPhpunit('<11')]
 class MacroExtensionTest extends AbstractTestCase
 {
     private function mockReflectionProvider()
@@ -71,7 +72,6 @@ public function testHasMacro()
         $this->assertFalse($scanner->hasMethod(CarbonInterface::class, 'foo'));
     }
 
-    #[RequiresPhpunit('<11')]
     public function testGetMacro()
     {
         $scanner = new MacroScanner($this->mockReflectionProvider());

From 41b550c65ff3fd05f97d1ce483afd551373920de Mon Sep 17 00:00:00 2001
From: kylekatarnls <kylekatarnls@gmail.com>
Date: Wed, 27 Mar 2024 16:37:43 +0100
Subject: [PATCH 5/5] Implement UTC variants for add/sub methods

---
 .github/workflows/tests.yml          |   2 +
 phpdoc.php                           |   6 +
 phpstan.neon                         |   1 +
 src/Carbon/Carbon.php                | 135 ++++++++++++----------
 src/Carbon/CarbonImmutable.php       | 135 ++++++++++++----------
 src/Carbon/CarbonInterface.php       | 161 +++++++++++++++++----------
 src/Carbon/Traits/Date.php           | 153 ++++++++++++++-----------
 tests/Carbon/IsTest.php              |   2 -
 tests/Carbon/ModifyTest.php          |  13 ++-
 tests/CarbonImmutable/IsTest.php     |   2 -
 tests/CarbonImmutable/ModifyTest.php |   2 -
 tests/CarbonInterval/AddTest.php     |   2 -
 12 files changed, 361 insertions(+), 253 deletions(-)

diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 6bef6abd52..5e038050f1 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -63,6 +63,7 @@ jobs:
 
       - name: Select PHPUnit version
         if: matrix.phpunit
+        shell: bash
         run: composer require --no-update --no-interaction --dev "phpunit/phpunit:^${{ matrix.phpunit }}"
 
       - name: Remove conflicting optional dependencies
@@ -71,6 +72,7 @@ jobs:
 
       - name: Downgrade nikic/php-parser
         if: matrix.phpunit < 11
+        shell: bash
         run: composer require --no-update --no-interaction --dev "nikic/php-parser:^4"
 
       - name: Install dependencies
diff --git a/phpdoc.php b/phpdoc.php
index 1797797211..8c2568737b 100644
--- a/phpdoc.php
+++ b/phpdoc.php
@@ -453,6 +453,12 @@ function dumpParameter(string $method, ReflectionParameter $parameter): string
                         $plUnit.'Until($endDate = null, int|float $factor = 1)',
                         "Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each $unitName or every X $plUnitName if a factor is given.",
                     ];
+                    $autoDocLines[] = [
+                        '@method',
+                        'float',
+                        'diffInUTC'.ucFirst($plUnit).'(DateTimeInterface|string|null $date, bool $absolute = false)',
+                        "Convert current and given date in UTC timezone and return a floating number of $plUnitName.",
+                    ];
 
                     break;
 
diff --git a/phpstan.neon b/phpstan.neon
index 792ed9fa20..bd6c822135 100644
--- a/phpstan.neon
+++ b/phpstan.neon
@@ -18,6 +18,7 @@ parameters:
         - '#^Call to an undefined static method#'
         - '#^Call to an undefined method Carbon\\Carbon(Immutable)?::floatDiffIn([A-Za-z]+)\(\)\.$#'
         - '#^Call to an undefined method Carbon\\Carbon(Immutable)?::diffInReal([A-Za-z]+)\(\)\.$#'
+        - '#^Call to an undefined method Carbon\\Carbon(Immutable)?::(add|sub)Real([A-Za-z]+)\(\)\.$#'
         - '#^Unsafe usage of new static\(\)\.$#'
         - '#^Method Carbon\\Carbon(Interface|Immutable)?::(add|sub)[A-Z][A-Za-z]+\(\) invoked with 1 parameter, 0 required\.$#'
         - '#^Call to an undefined method Carbon\\Carbon(Interface|Immutable)?::(super|noThis|toAppTz|copyWithAppTz)\(\)\.$#'
diff --git a/src/Carbon/Carbon.php b/src/Carbon/Carbon.php
index 298100583b..8364e84125 100644
--- a/src/Carbon/Carbon.php
+++ b/src/Carbon/Carbon.php
@@ -506,81 +506,96 @@
  * @method        $this            addWeekday()                                                                       Add one weekday to the instance (using date interval).
  * @method        $this            subWeekdays(int|float $value = 1)                                                  Sub weekdays (the $value count passed in) to the instance (using date interval).
  * @method        $this            subWeekday()                                                                       Sub one weekday to the instance (using date interval).
- * @method        $this            addRealMicros(int|float $value = 1)                                                Add microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealMicro()                                                                     Add one microsecond to the instance (using timestamp).
- * @method        $this            subRealMicros(int|float $value = 1)                                                Sub microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealMicro()                                                                     Sub one microsecond to the instance (using timestamp).
+ * @method        $this            addUTCMicros(int|float $value = 1)                                                 Add microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCMicro()                                                                      Add one microsecond to the instance (using timestamp).
+ * @method        $this            subUTCMicros(int|float $value = 1)                                                 Sub microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCMicro()                                                                      Sub one microsecond to the instance (using timestamp).
  * @method        CarbonPeriod     microsUntil($endDate = null, int|float $factor = 1)                                Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each microsecond or every X microseconds if a factor is given.
- * @method        $this            addRealMicroseconds(int|float $value = 1)                                          Add microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealMicrosecond()                                                               Add one microsecond to the instance (using timestamp).
- * @method        $this            subRealMicroseconds(int|float $value = 1)                                          Sub microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealMicrosecond()                                                               Sub one microsecond to the instance (using timestamp).
+ * @method        float            diffInUTCMicros(DateTimeInterface|string|null $date, bool $absolute = false)       Convert current and given date in UTC timezone and return a floating number of microseconds.
+ * @method        $this            addUTCMicroseconds(int|float $value = 1)                                           Add microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCMicrosecond()                                                                Add one microsecond to the instance (using timestamp).
+ * @method        $this            subUTCMicroseconds(int|float $value = 1)                                           Sub microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCMicrosecond()                                                                Sub one microsecond to the instance (using timestamp).
  * @method        CarbonPeriod     microsecondsUntil($endDate = null, int|float $factor = 1)                          Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each microsecond or every X microseconds if a factor is given.
- * @method        $this            addRealMillis(int|float $value = 1)                                                Add milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealMilli()                                                                     Add one millisecond to the instance (using timestamp).
- * @method        $this            subRealMillis(int|float $value = 1)                                                Sub milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealMilli()                                                                     Sub one millisecond to the instance (using timestamp).
+ * @method        float            diffInUTCMicroseconds(DateTimeInterface|string|null $date, bool $absolute = false) Convert current and given date in UTC timezone and return a floating number of microseconds.
+ * @method        $this            addUTCMillis(int|float $value = 1)                                                 Add milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCMilli()                                                                      Add one millisecond to the instance (using timestamp).
+ * @method        $this            subUTCMillis(int|float $value = 1)                                                 Sub milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCMilli()                                                                      Sub one millisecond to the instance (using timestamp).
  * @method        CarbonPeriod     millisUntil($endDate = null, int|float $factor = 1)                                Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each millisecond or every X milliseconds if a factor is given.
- * @method        $this            addRealMilliseconds(int|float $value = 1)                                          Add milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealMillisecond()                                                               Add one millisecond to the instance (using timestamp).
- * @method        $this            subRealMilliseconds(int|float $value = 1)                                          Sub milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealMillisecond()                                                               Sub one millisecond to the instance (using timestamp).
+ * @method        float            diffInUTCMillis(DateTimeInterface|string|null $date, bool $absolute = false)       Convert current and given date in UTC timezone and return a floating number of milliseconds.
+ * @method        $this            addUTCMilliseconds(int|float $value = 1)                                           Add milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCMillisecond()                                                                Add one millisecond to the instance (using timestamp).
+ * @method        $this            subUTCMilliseconds(int|float $value = 1)                                           Sub milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCMillisecond()                                                                Sub one millisecond to the instance (using timestamp).
  * @method        CarbonPeriod     millisecondsUntil($endDate = null, int|float $factor = 1)                          Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each millisecond or every X milliseconds if a factor is given.
- * @method        $this            addRealSeconds(int|float $value = 1)                                               Add seconds (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealSecond()                                                                    Add one second to the instance (using timestamp).
- * @method        $this            subRealSeconds(int|float $value = 1)                                               Sub seconds (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealSecond()                                                                    Sub one second to the instance (using timestamp).
+ * @method        float            diffInUTCMilliseconds(DateTimeInterface|string|null $date, bool $absolute = false) Convert current and given date in UTC timezone and return a floating number of milliseconds.
+ * @method        $this            addUTCSeconds(int|float $value = 1)                                                Add seconds (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCSecond()                                                                     Add one second to the instance (using timestamp).
+ * @method        $this            subUTCSeconds(int|float $value = 1)                                                Sub seconds (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCSecond()                                                                     Sub one second to the instance (using timestamp).
  * @method        CarbonPeriod     secondsUntil($endDate = null, int|float $factor = 1)                               Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each second or every X seconds if a factor is given.
- * @method        $this            addRealMinutes(int|float $value = 1)                                               Add minutes (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealMinute()                                                                    Add one minute to the instance (using timestamp).
- * @method        $this            subRealMinutes(int|float $value = 1)                                               Sub minutes (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealMinute()                                                                    Sub one minute to the instance (using timestamp).
+ * @method        float            diffInUTCSeconds(DateTimeInterface|string|null $date, bool $absolute = false)      Convert current and given date in UTC timezone and return a floating number of seconds.
+ * @method        $this            addUTCMinutes(int|float $value = 1)                                                Add minutes (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCMinute()                                                                     Add one minute to the instance (using timestamp).
+ * @method        $this            subUTCMinutes(int|float $value = 1)                                                Sub minutes (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCMinute()                                                                     Sub one minute to the instance (using timestamp).
  * @method        CarbonPeriod     minutesUntil($endDate = null, int|float $factor = 1)                               Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each minute or every X minutes if a factor is given.
- * @method        $this            addRealHours(int|float $value = 1)                                                 Add hours (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealHour()                                                                      Add one hour to the instance (using timestamp).
- * @method        $this            subRealHours(int|float $value = 1)                                                 Sub hours (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealHour()                                                                      Sub one hour to the instance (using timestamp).
+ * @method        float            diffInUTCMinutes(DateTimeInterface|string|null $date, bool $absolute = false)      Convert current and given date in UTC timezone and return a floating number of minutes.
+ * @method        $this            addUTCHours(int|float $value = 1)                                                  Add hours (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCHour()                                                                       Add one hour to the instance (using timestamp).
+ * @method        $this            subUTCHours(int|float $value = 1)                                                  Sub hours (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCHour()                                                                       Sub one hour to the instance (using timestamp).
  * @method        CarbonPeriod     hoursUntil($endDate = null, int|float $factor = 1)                                 Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each hour or every X hours if a factor is given.
- * @method        $this            addRealDays(int|float $value = 1)                                                  Add days (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealDay()                                                                       Add one day to the instance (using timestamp).
- * @method        $this            subRealDays(int|float $value = 1)                                                  Sub days (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealDay()                                                                       Sub one day to the instance (using timestamp).
+ * @method        float            diffInUTCHours(DateTimeInterface|string|null $date, bool $absolute = false)        Convert current and given date in UTC timezone and return a floating number of hours.
+ * @method        $this            addUTCDays(int|float $value = 1)                                                   Add days (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCDay()                                                                        Add one day to the instance (using timestamp).
+ * @method        $this            subUTCDays(int|float $value = 1)                                                   Sub days (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCDay()                                                                        Sub one day to the instance (using timestamp).
  * @method        CarbonPeriod     daysUntil($endDate = null, int|float $factor = 1)                                  Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each day or every X days if a factor is given.
- * @method        $this            addRealWeeks(int|float $value = 1)                                                 Add weeks (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealWeek()                                                                      Add one week to the instance (using timestamp).
- * @method        $this            subRealWeeks(int|float $value = 1)                                                 Sub weeks (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealWeek()                                                                      Sub one week to the instance (using timestamp).
+ * @method        float            diffInUTCDays(DateTimeInterface|string|null $date, bool $absolute = false)         Convert current and given date in UTC timezone and return a floating number of days.
+ * @method        $this            addUTCWeeks(int|float $value = 1)                                                  Add weeks (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCWeek()                                                                       Add one week to the instance (using timestamp).
+ * @method        $this            subUTCWeeks(int|float $value = 1)                                                  Sub weeks (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCWeek()                                                                       Sub one week to the instance (using timestamp).
  * @method        CarbonPeriod     weeksUntil($endDate = null, int|float $factor = 1)                                 Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each week or every X weeks if a factor is given.
- * @method        $this            addRealMonths(int|float $value = 1)                                                Add months (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealMonth()                                                                     Add one month to the instance (using timestamp).
- * @method        $this            subRealMonths(int|float $value = 1)                                                Sub months (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealMonth()                                                                     Sub one month to the instance (using timestamp).
+ * @method        float            diffInUTCWeeks(DateTimeInterface|string|null $date, bool $absolute = false)        Convert current and given date in UTC timezone and return a floating number of weeks.
+ * @method        $this            addUTCMonths(int|float $value = 1)                                                 Add months (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCMonth()                                                                      Add one month to the instance (using timestamp).
+ * @method        $this            subUTCMonths(int|float $value = 1)                                                 Sub months (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCMonth()                                                                      Sub one month to the instance (using timestamp).
  * @method        CarbonPeriod     monthsUntil($endDate = null, int|float $factor = 1)                                Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each month or every X months if a factor is given.
- * @method        $this            addRealQuarters(int|float $value = 1)                                              Add quarters (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealQuarter()                                                                   Add one quarter to the instance (using timestamp).
- * @method        $this            subRealQuarters(int|float $value = 1)                                              Sub quarters (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealQuarter()                                                                   Sub one quarter to the instance (using timestamp).
+ * @method        float            diffInUTCMonths(DateTimeInterface|string|null $date, bool $absolute = false)       Convert current and given date in UTC timezone and return a floating number of months.
+ * @method        $this            addUTCQuarters(int|float $value = 1)                                               Add quarters (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCQuarter()                                                                    Add one quarter to the instance (using timestamp).
+ * @method        $this            subUTCQuarters(int|float $value = 1)                                               Sub quarters (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCQuarter()                                                                    Sub one quarter to the instance (using timestamp).
  * @method        CarbonPeriod     quartersUntil($endDate = null, int|float $factor = 1)                              Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each quarter or every X quarters if a factor is given.
- * @method        $this            addRealYears(int|float $value = 1)                                                 Add years (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealYear()                                                                      Add one year to the instance (using timestamp).
- * @method        $this            subRealYears(int|float $value = 1)                                                 Sub years (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealYear()                                                                      Sub one year to the instance (using timestamp).
+ * @method        float            diffInUTCQuarters(DateTimeInterface|string|null $date, bool $absolute = false)     Convert current and given date in UTC timezone and return a floating number of quarters.
+ * @method        $this            addUTCYears(int|float $value = 1)                                                  Add years (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCYear()                                                                       Add one year to the instance (using timestamp).
+ * @method        $this            subUTCYears(int|float $value = 1)                                                  Sub years (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCYear()                                                                       Sub one year to the instance (using timestamp).
  * @method        CarbonPeriod     yearsUntil($endDate = null, int|float $factor = 1)                                 Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each year or every X years if a factor is given.
- * @method        $this            addRealDecades(int|float $value = 1)                                               Add decades (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealDecade()                                                                    Add one decade to the instance (using timestamp).
- * @method        $this            subRealDecades(int|float $value = 1)                                               Sub decades (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealDecade()                                                                    Sub one decade to the instance (using timestamp).
+ * @method        float            diffInUTCYears(DateTimeInterface|string|null $date, bool $absolute = false)        Convert current and given date in UTC timezone and return a floating number of years.
+ * @method        $this            addUTCDecades(int|float $value = 1)                                                Add decades (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCDecade()                                                                     Add one decade to the instance (using timestamp).
+ * @method        $this            subUTCDecades(int|float $value = 1)                                                Sub decades (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCDecade()                                                                     Sub one decade to the instance (using timestamp).
  * @method        CarbonPeriod     decadesUntil($endDate = null, int|float $factor = 1)                               Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each decade or every X decades if a factor is given.
- * @method        $this            addRealCenturies(int|float $value = 1)                                             Add centuries (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealCentury()                                                                   Add one century to the instance (using timestamp).
- * @method        $this            subRealCenturies(int|float $value = 1)                                             Sub centuries (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealCentury()                                                                   Sub one century to the instance (using timestamp).
+ * @method        float            diffInUTCDecades(DateTimeInterface|string|null $date, bool $absolute = false)      Convert current and given date in UTC timezone and return a floating number of decades.
+ * @method        $this            addUTCCenturies(int|float $value = 1)                                              Add centuries (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCCentury()                                                                    Add one century to the instance (using timestamp).
+ * @method        $this            subUTCCenturies(int|float $value = 1)                                              Sub centuries (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCCentury()                                                                    Sub one century to the instance (using timestamp).
  * @method        CarbonPeriod     centuriesUntil($endDate = null, int|float $factor = 1)                             Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each century or every X centuries if a factor is given.
- * @method        $this            addRealMillennia(int|float $value = 1)                                             Add millennia (the $value count passed in) to the instance (using timestamp).
- * @method        $this            addRealMillennium()                                                                Add one millennium to the instance (using timestamp).
- * @method        $this            subRealMillennia(int|float $value = 1)                                             Sub millennia (the $value count passed in) to the instance (using timestamp).
- * @method        $this            subRealMillennium()                                                                Sub one millennium to the instance (using timestamp).
+ * @method        float            diffInUTCCenturies(DateTimeInterface|string|null $date, bool $absolute = false)    Convert current and given date in UTC timezone and return a floating number of centuries.
+ * @method        $this            addUTCMillennia(int|float $value = 1)                                              Add millennia (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            addUTCMillennium()                                                                 Add one millennium to the instance (using timestamp).
+ * @method        $this            subUTCMillennia(int|float $value = 1)                                              Sub millennia (the $value count passed in) to the instance (using timestamp).
+ * @method        $this            subUTCMillennium()                                                                 Sub one millennium to the instance (using timestamp).
  * @method        CarbonPeriod     millenniaUntil($endDate = null, int|float $factor = 1)                             Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each millennium or every X millennia if a factor is given.
+ * @method        float            diffInUTCMillennia(DateTimeInterface|string|null $date, bool $absolute = false)    Convert current and given date in UTC timezone and return a floating number of millennia.
  * @method        $this            roundYear(float $precision = 1, string $function = "round")                        Round the current instance year with given precision using the given function.
  * @method        $this            roundYears(float $precision = 1, string $function = "round")                       Round the current instance year with given precision using the given function.
  * @method        $this            floorYear(float $precision = 1)                                                    Truncate the current instance year with given precision.
diff --git a/src/Carbon/CarbonImmutable.php b/src/Carbon/CarbonImmutable.php
index ff0c87aa40..ee8cb1559c 100644
--- a/src/Carbon/CarbonImmutable.php
+++ b/src/Carbon/CarbonImmutable.php
@@ -506,81 +506,96 @@
  * @method        CarbonImmutable  addWeekday()                                                                       Add one weekday to the instance (using date interval).
  * @method        CarbonImmutable  subWeekdays(int|float $value = 1)                                                  Sub weekdays (the $value count passed in) to the instance (using date interval).
  * @method        CarbonImmutable  subWeekday()                                                                       Sub one weekday to the instance (using date interval).
- * @method        CarbonImmutable  addRealMicros(int|float $value = 1)                                                Add microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealMicro()                                                                     Add one microsecond to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMicros(int|float $value = 1)                                                Sub microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMicro()                                                                     Sub one microsecond to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCMicros(int|float $value = 1)                                                 Add microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCMicro()                                                                      Add one microsecond to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMicros(int|float $value = 1)                                                 Sub microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMicro()                                                                      Sub one microsecond to the instance (using timestamp).
  * @method        CarbonPeriod     microsUntil($endDate = null, int|float $factor = 1)                                Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each microsecond or every X microseconds if a factor is given.
- * @method        CarbonImmutable  addRealMicroseconds(int|float $value = 1)                                          Add microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealMicrosecond()                                                               Add one microsecond to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMicroseconds(int|float $value = 1)                                          Sub microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMicrosecond()                                                               Sub one microsecond to the instance (using timestamp).
+ * @method        float            diffInUTCMicros(DateTimeInterface|string|null $date, bool $absolute = false)       Convert current and given date in UTC timezone and return a floating number of microseconds.
+ * @method        CarbonImmutable  addUTCMicroseconds(int|float $value = 1)                                           Add microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCMicrosecond()                                                                Add one microsecond to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMicroseconds(int|float $value = 1)                                           Sub microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMicrosecond()                                                                Sub one microsecond to the instance (using timestamp).
  * @method        CarbonPeriod     microsecondsUntil($endDate = null, int|float $factor = 1)                          Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each microsecond or every X microseconds if a factor is given.
- * @method        CarbonImmutable  addRealMillis(int|float $value = 1)                                                Add milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealMilli()                                                                     Add one millisecond to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMillis(int|float $value = 1)                                                Sub milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMilli()                                                                     Sub one millisecond to the instance (using timestamp).
+ * @method        float            diffInUTCMicroseconds(DateTimeInterface|string|null $date, bool $absolute = false) Convert current and given date in UTC timezone and return a floating number of microseconds.
+ * @method        CarbonImmutable  addUTCMillis(int|float $value = 1)                                                 Add milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCMilli()                                                                      Add one millisecond to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMillis(int|float $value = 1)                                                 Sub milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMilli()                                                                      Sub one millisecond to the instance (using timestamp).
  * @method        CarbonPeriod     millisUntil($endDate = null, int|float $factor = 1)                                Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each millisecond or every X milliseconds if a factor is given.
- * @method        CarbonImmutable  addRealMilliseconds(int|float $value = 1)                                          Add milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealMillisecond()                                                               Add one millisecond to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMilliseconds(int|float $value = 1)                                          Sub milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMillisecond()                                                               Sub one millisecond to the instance (using timestamp).
+ * @method        float            diffInUTCMillis(DateTimeInterface|string|null $date, bool $absolute = false)       Convert current and given date in UTC timezone and return a floating number of milliseconds.
+ * @method        CarbonImmutable  addUTCMilliseconds(int|float $value = 1)                                           Add milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCMillisecond()                                                                Add one millisecond to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMilliseconds(int|float $value = 1)                                           Sub milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMillisecond()                                                                Sub one millisecond to the instance (using timestamp).
  * @method        CarbonPeriod     millisecondsUntil($endDate = null, int|float $factor = 1)                          Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each millisecond or every X milliseconds if a factor is given.
- * @method        CarbonImmutable  addRealSeconds(int|float $value = 1)                                               Add seconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealSecond()                                                                    Add one second to the instance (using timestamp).
- * @method        CarbonImmutable  subRealSeconds(int|float $value = 1)                                               Sub seconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealSecond()                                                                    Sub one second to the instance (using timestamp).
+ * @method        float            diffInUTCMilliseconds(DateTimeInterface|string|null $date, bool $absolute = false) Convert current and given date in UTC timezone and return a floating number of milliseconds.
+ * @method        CarbonImmutable  addUTCSeconds(int|float $value = 1)                                                Add seconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCSecond()                                                                     Add one second to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCSeconds(int|float $value = 1)                                                Sub seconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCSecond()                                                                     Sub one second to the instance (using timestamp).
  * @method        CarbonPeriod     secondsUntil($endDate = null, int|float $factor = 1)                               Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each second or every X seconds if a factor is given.
- * @method        CarbonImmutable  addRealMinutes(int|float $value = 1)                                               Add minutes (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealMinute()                                                                    Add one minute to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMinutes(int|float $value = 1)                                               Sub minutes (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMinute()                                                                    Sub one minute to the instance (using timestamp).
+ * @method        float            diffInUTCSeconds(DateTimeInterface|string|null $date, bool $absolute = false)      Convert current and given date in UTC timezone and return a floating number of seconds.
+ * @method        CarbonImmutable  addUTCMinutes(int|float $value = 1)                                                Add minutes (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCMinute()                                                                     Add one minute to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMinutes(int|float $value = 1)                                                Sub minutes (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMinute()                                                                     Sub one minute to the instance (using timestamp).
  * @method        CarbonPeriod     minutesUntil($endDate = null, int|float $factor = 1)                               Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each minute or every X minutes if a factor is given.
- * @method        CarbonImmutable  addRealHours(int|float $value = 1)                                                 Add hours (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealHour()                                                                      Add one hour to the instance (using timestamp).
- * @method        CarbonImmutable  subRealHours(int|float $value = 1)                                                 Sub hours (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealHour()                                                                      Sub one hour to the instance (using timestamp).
+ * @method        float            diffInUTCMinutes(DateTimeInterface|string|null $date, bool $absolute = false)      Convert current and given date in UTC timezone and return a floating number of minutes.
+ * @method        CarbonImmutable  addUTCHours(int|float $value = 1)                                                  Add hours (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCHour()                                                                       Add one hour to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCHours(int|float $value = 1)                                                  Sub hours (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCHour()                                                                       Sub one hour to the instance (using timestamp).
  * @method        CarbonPeriod     hoursUntil($endDate = null, int|float $factor = 1)                                 Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each hour or every X hours if a factor is given.
- * @method        CarbonImmutable  addRealDays(int|float $value = 1)                                                  Add days (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealDay()                                                                       Add one day to the instance (using timestamp).
- * @method        CarbonImmutable  subRealDays(int|float $value = 1)                                                  Sub days (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealDay()                                                                       Sub one day to the instance (using timestamp).
+ * @method        float            diffInUTCHours(DateTimeInterface|string|null $date, bool $absolute = false)        Convert current and given date in UTC timezone and return a floating number of hours.
+ * @method        CarbonImmutable  addUTCDays(int|float $value = 1)                                                   Add days (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCDay()                                                                        Add one day to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCDays(int|float $value = 1)                                                   Sub days (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCDay()                                                                        Sub one day to the instance (using timestamp).
  * @method        CarbonPeriod     daysUntil($endDate = null, int|float $factor = 1)                                  Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each day or every X days if a factor is given.
- * @method        CarbonImmutable  addRealWeeks(int|float $value = 1)                                                 Add weeks (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealWeek()                                                                      Add one week to the instance (using timestamp).
- * @method        CarbonImmutable  subRealWeeks(int|float $value = 1)                                                 Sub weeks (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealWeek()                                                                      Sub one week to the instance (using timestamp).
+ * @method        float            diffInUTCDays(DateTimeInterface|string|null $date, bool $absolute = false)         Convert current and given date in UTC timezone and return a floating number of days.
+ * @method        CarbonImmutable  addUTCWeeks(int|float $value = 1)                                                  Add weeks (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCWeek()                                                                       Add one week to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCWeeks(int|float $value = 1)                                                  Sub weeks (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCWeek()                                                                       Sub one week to the instance (using timestamp).
  * @method        CarbonPeriod     weeksUntil($endDate = null, int|float $factor = 1)                                 Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each week or every X weeks if a factor is given.
- * @method        CarbonImmutable  addRealMonths(int|float $value = 1)                                                Add months (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealMonth()                                                                     Add one month to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMonths(int|float $value = 1)                                                Sub months (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMonth()                                                                     Sub one month to the instance (using timestamp).
+ * @method        float            diffInUTCWeeks(DateTimeInterface|string|null $date, bool $absolute = false)        Convert current and given date in UTC timezone and return a floating number of weeks.
+ * @method        CarbonImmutable  addUTCMonths(int|float $value = 1)                                                 Add months (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCMonth()                                                                      Add one month to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMonths(int|float $value = 1)                                                 Sub months (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMonth()                                                                      Sub one month to the instance (using timestamp).
  * @method        CarbonPeriod     monthsUntil($endDate = null, int|float $factor = 1)                                Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each month or every X months if a factor is given.
- * @method        CarbonImmutable  addRealQuarters(int|float $value = 1)                                              Add quarters (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealQuarter()                                                                   Add one quarter to the instance (using timestamp).
- * @method        CarbonImmutable  subRealQuarters(int|float $value = 1)                                              Sub quarters (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealQuarter()                                                                   Sub one quarter to the instance (using timestamp).
+ * @method        float            diffInUTCMonths(DateTimeInterface|string|null $date, bool $absolute = false)       Convert current and given date in UTC timezone and return a floating number of months.
+ * @method        CarbonImmutable  addUTCQuarters(int|float $value = 1)                                               Add quarters (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCQuarter()                                                                    Add one quarter to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCQuarters(int|float $value = 1)                                               Sub quarters (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCQuarter()                                                                    Sub one quarter to the instance (using timestamp).
  * @method        CarbonPeriod     quartersUntil($endDate = null, int|float $factor = 1)                              Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each quarter or every X quarters if a factor is given.
- * @method        CarbonImmutable  addRealYears(int|float $value = 1)                                                 Add years (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealYear()                                                                      Add one year to the instance (using timestamp).
- * @method        CarbonImmutable  subRealYears(int|float $value = 1)                                                 Sub years (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealYear()                                                                      Sub one year to the instance (using timestamp).
+ * @method        float            diffInUTCQuarters(DateTimeInterface|string|null $date, bool $absolute = false)     Convert current and given date in UTC timezone and return a floating number of quarters.
+ * @method        CarbonImmutable  addUTCYears(int|float $value = 1)                                                  Add years (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCYear()                                                                       Add one year to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCYears(int|float $value = 1)                                                  Sub years (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCYear()                                                                       Sub one year to the instance (using timestamp).
  * @method        CarbonPeriod     yearsUntil($endDate = null, int|float $factor = 1)                                 Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each year or every X years if a factor is given.
- * @method        CarbonImmutable  addRealDecades(int|float $value = 1)                                               Add decades (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealDecade()                                                                    Add one decade to the instance (using timestamp).
- * @method        CarbonImmutable  subRealDecades(int|float $value = 1)                                               Sub decades (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealDecade()                                                                    Sub one decade to the instance (using timestamp).
+ * @method        float            diffInUTCYears(DateTimeInterface|string|null $date, bool $absolute = false)        Convert current and given date in UTC timezone and return a floating number of years.
+ * @method        CarbonImmutable  addUTCDecades(int|float $value = 1)                                                Add decades (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCDecade()                                                                     Add one decade to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCDecades(int|float $value = 1)                                                Sub decades (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCDecade()                                                                     Sub one decade to the instance (using timestamp).
  * @method        CarbonPeriod     decadesUntil($endDate = null, int|float $factor = 1)                               Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each decade or every X decades if a factor is given.
- * @method        CarbonImmutable  addRealCenturies(int|float $value = 1)                                             Add centuries (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealCentury()                                                                   Add one century to the instance (using timestamp).
- * @method        CarbonImmutable  subRealCenturies(int|float $value = 1)                                             Sub centuries (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealCentury()                                                                   Sub one century to the instance (using timestamp).
+ * @method        float            diffInUTCDecades(DateTimeInterface|string|null $date, bool $absolute = false)      Convert current and given date in UTC timezone and return a floating number of decades.
+ * @method        CarbonImmutable  addUTCCenturies(int|float $value = 1)                                              Add centuries (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCCentury()                                                                    Add one century to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCCenturies(int|float $value = 1)                                              Sub centuries (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCCentury()                                                                    Sub one century to the instance (using timestamp).
  * @method        CarbonPeriod     centuriesUntil($endDate = null, int|float $factor = 1)                             Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each century or every X centuries if a factor is given.
- * @method        CarbonImmutable  addRealMillennia(int|float $value = 1)                                             Add millennia (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  addRealMillennium()                                                                Add one millennium to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMillennia(int|float $value = 1)                                             Sub millennia (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonImmutable  subRealMillennium()                                                                Sub one millennium to the instance (using timestamp).
+ * @method        float            diffInUTCCenturies(DateTimeInterface|string|null $date, bool $absolute = false)    Convert current and given date in UTC timezone and return a floating number of centuries.
+ * @method        CarbonImmutable  addUTCMillennia(int|float $value = 1)                                              Add millennia (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  addUTCMillennium()                                                                 Add one millennium to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMillennia(int|float $value = 1)                                              Sub millennia (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonImmutable  subUTCMillennium()                                                                 Sub one millennium to the instance (using timestamp).
  * @method        CarbonPeriod     millenniaUntil($endDate = null, int|float $factor = 1)                             Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each millennium or every X millennia if a factor is given.
+ * @method        float            diffInUTCMillennia(DateTimeInterface|string|null $date, bool $absolute = false)    Convert current and given date in UTC timezone and return a floating number of millennia.
  * @method        CarbonImmutable  roundYear(float $precision = 1, string $function = "round")                        Round the current instance year with given precision using the given function.
  * @method        CarbonImmutable  roundYears(float $precision = 1, string $function = "round")                       Round the current instance year with given precision using the given function.
  * @method        CarbonImmutable  floorYear(float $precision = 1)                                                    Truncate the current instance year with given precision.
diff --git a/src/Carbon/CarbonInterface.php b/src/Carbon/CarbonInterface.php
index f24311c463..2399260415 100644
--- a/src/Carbon/CarbonInterface.php
+++ b/src/Carbon/CarbonInterface.php
@@ -522,81 +522,96 @@
  * @method        CarbonInterface  addWeekday()                                                                       Add one weekday to the instance (using date interval).
  * @method        CarbonInterface  subWeekdays(int|float $value = 1)                                                  Sub weekdays (the $value count passed in) to the instance (using date interval).
  * @method        CarbonInterface  subWeekday()                                                                       Sub one weekday to the instance (using date interval).
- * @method        CarbonInterface  addRealMicros(int|float $value = 1)                                                Add microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMicro()                                                                     Add one microsecond to the instance (using timestamp).
- * @method        CarbonInterface  subRealMicros(int|float $value = 1)                                                Sub microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMicro()                                                                     Sub one microsecond to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMicros(int|float $value = 1)                                                 Add microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMicro()                                                                      Add one microsecond to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMicros(int|float $value = 1)                                                 Sub microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMicro()                                                                      Sub one microsecond to the instance (using timestamp).
  * @method        CarbonPeriod     microsUntil($endDate = null, int|float $factor = 1)                                Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each microsecond or every X microseconds if a factor is given.
- * @method        CarbonInterface  addRealMicroseconds(int|float $value = 1)                                          Add microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMicrosecond()                                                               Add one microsecond to the instance (using timestamp).
- * @method        CarbonInterface  subRealMicroseconds(int|float $value = 1)                                          Sub microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMicrosecond()                                                               Sub one microsecond to the instance (using timestamp).
+ * @method        float            diffInUTCMicros(DateTimeInterface|string|null $date, bool $absolute = false)       Convert current and given date in UTC timezone and return a floating number of microseconds.
+ * @method        CarbonInterface  addUTCMicroseconds(int|float $value = 1)                                           Add microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMicrosecond()                                                                Add one microsecond to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMicroseconds(int|float $value = 1)                                           Sub microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMicrosecond()                                                                Sub one microsecond to the instance (using timestamp).
  * @method        CarbonPeriod     microsecondsUntil($endDate = null, int|float $factor = 1)                          Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each microsecond or every X microseconds if a factor is given.
- * @method        CarbonInterface  addRealMillis(int|float $value = 1)                                                Add milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMilli()                                                                     Add one millisecond to the instance (using timestamp).
- * @method        CarbonInterface  subRealMillis(int|float $value = 1)                                                Sub milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMilli()                                                                     Sub one millisecond to the instance (using timestamp).
+ * @method        float            diffInUTCMicroseconds(DateTimeInterface|string|null $date, bool $absolute = false) Convert current and given date in UTC timezone and return a floating number of microseconds.
+ * @method        CarbonInterface  addUTCMillis(int|float $value = 1)                                                 Add milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMilli()                                                                      Add one millisecond to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMillis(int|float $value = 1)                                                 Sub milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMilli()                                                                      Sub one millisecond to the instance (using timestamp).
  * @method        CarbonPeriod     millisUntil($endDate = null, int|float $factor = 1)                                Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each millisecond or every X milliseconds if a factor is given.
- * @method        CarbonInterface  addRealMilliseconds(int|float $value = 1)                                          Add milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMillisecond()                                                               Add one millisecond to the instance (using timestamp).
- * @method        CarbonInterface  subRealMilliseconds(int|float $value = 1)                                          Sub milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMillisecond()                                                               Sub one millisecond to the instance (using timestamp).
+ * @method        float            diffInUTCMillis(DateTimeInterface|string|null $date, bool $absolute = false)       Convert current and given date in UTC timezone and return a floating number of milliseconds.
+ * @method        CarbonInterface  addUTCMilliseconds(int|float $value = 1)                                           Add milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMillisecond()                                                                Add one millisecond to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMilliseconds(int|float $value = 1)                                           Sub milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMillisecond()                                                                Sub one millisecond to the instance (using timestamp).
  * @method        CarbonPeriod     millisecondsUntil($endDate = null, int|float $factor = 1)                          Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each millisecond or every X milliseconds if a factor is given.
- * @method        CarbonInterface  addRealSeconds(int|float $value = 1)                                               Add seconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealSecond()                                                                    Add one second to the instance (using timestamp).
- * @method        CarbonInterface  subRealSeconds(int|float $value = 1)                                               Sub seconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealSecond()                                                                    Sub one second to the instance (using timestamp).
+ * @method        float            diffInUTCMilliseconds(DateTimeInterface|string|null $date, bool $absolute = false) Convert current and given date in UTC timezone and return a floating number of milliseconds.
+ * @method        CarbonInterface  addUTCSeconds(int|float $value = 1)                                                Add seconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCSecond()                                                                     Add one second to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCSeconds(int|float $value = 1)                                                Sub seconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCSecond()                                                                     Sub one second to the instance (using timestamp).
  * @method        CarbonPeriod     secondsUntil($endDate = null, int|float $factor = 1)                               Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each second or every X seconds if a factor is given.
- * @method        CarbonInterface  addRealMinutes(int|float $value = 1)                                               Add minutes (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMinute()                                                                    Add one minute to the instance (using timestamp).
- * @method        CarbonInterface  subRealMinutes(int|float $value = 1)                                               Sub minutes (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMinute()                                                                    Sub one minute to the instance (using timestamp).
+ * @method        float            diffInUTCSeconds(DateTimeInterface|string|null $date, bool $absolute = false)      Convert current and given date in UTC timezone and return a floating number of seconds.
+ * @method        CarbonInterface  addUTCMinutes(int|float $value = 1)                                                Add minutes (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMinute()                                                                     Add one minute to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMinutes(int|float $value = 1)                                                Sub minutes (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMinute()                                                                     Sub one minute to the instance (using timestamp).
  * @method        CarbonPeriod     minutesUntil($endDate = null, int|float $factor = 1)                               Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each minute or every X minutes if a factor is given.
- * @method        CarbonInterface  addRealHours(int|float $value = 1)                                                 Add hours (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealHour()                                                                      Add one hour to the instance (using timestamp).
- * @method        CarbonInterface  subRealHours(int|float $value = 1)                                                 Sub hours (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealHour()                                                                      Sub one hour to the instance (using timestamp).
+ * @method        float            diffInUTCMinutes(DateTimeInterface|string|null $date, bool $absolute = false)      Convert current and given date in UTC timezone and return a floating number of minutes.
+ * @method        CarbonInterface  addUTCHours(int|float $value = 1)                                                  Add hours (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCHour()                                                                       Add one hour to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCHours(int|float $value = 1)                                                  Sub hours (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCHour()                                                                       Sub one hour to the instance (using timestamp).
  * @method        CarbonPeriod     hoursUntil($endDate = null, int|float $factor = 1)                                 Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each hour or every X hours if a factor is given.
- * @method        CarbonInterface  addRealDays(int|float $value = 1)                                                  Add days (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealDay()                                                                       Add one day to the instance (using timestamp).
- * @method        CarbonInterface  subRealDays(int|float $value = 1)                                                  Sub days (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealDay()                                                                       Sub one day to the instance (using timestamp).
+ * @method        float            diffInUTCHours(DateTimeInterface|string|null $date, bool $absolute = false)        Convert current and given date in UTC timezone and return a floating number of hours.
+ * @method        CarbonInterface  addUTCDays(int|float $value = 1)                                                   Add days (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCDay()                                                                        Add one day to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCDays(int|float $value = 1)                                                   Sub days (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCDay()                                                                        Sub one day to the instance (using timestamp).
  * @method        CarbonPeriod     daysUntil($endDate = null, int|float $factor = 1)                                  Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each day or every X days if a factor is given.
- * @method        CarbonInterface  addRealWeeks(int|float $value = 1)                                                 Add weeks (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealWeek()                                                                      Add one week to the instance (using timestamp).
- * @method        CarbonInterface  subRealWeeks(int|float $value = 1)                                                 Sub weeks (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealWeek()                                                                      Sub one week to the instance (using timestamp).
+ * @method        float            diffInUTCDays(DateTimeInterface|string|null $date, bool $absolute = false)         Convert current and given date in UTC timezone and return a floating number of days.
+ * @method        CarbonInterface  addUTCWeeks(int|float $value = 1)                                                  Add weeks (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCWeek()                                                                       Add one week to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCWeeks(int|float $value = 1)                                                  Sub weeks (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCWeek()                                                                       Sub one week to the instance (using timestamp).
  * @method        CarbonPeriod     weeksUntil($endDate = null, int|float $factor = 1)                                 Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each week or every X weeks if a factor is given.
- * @method        CarbonInterface  addRealMonths(int|float $value = 1)                                                Add months (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMonth()                                                                     Add one month to the instance (using timestamp).
- * @method        CarbonInterface  subRealMonths(int|float $value = 1)                                                Sub months (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMonth()                                                                     Sub one month to the instance (using timestamp).
+ * @method        float            diffInUTCWeeks(DateTimeInterface|string|null $date, bool $absolute = false)        Convert current and given date in UTC timezone and return a floating number of weeks.
+ * @method        CarbonInterface  addUTCMonths(int|float $value = 1)                                                 Add months (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMonth()                                                                      Add one month to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMonths(int|float $value = 1)                                                 Sub months (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMonth()                                                                      Sub one month to the instance (using timestamp).
  * @method        CarbonPeriod     monthsUntil($endDate = null, int|float $factor = 1)                                Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each month or every X months if a factor is given.
- * @method        CarbonInterface  addRealQuarters(int|float $value = 1)                                              Add quarters (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealQuarter()                                                                   Add one quarter to the instance (using timestamp).
- * @method        CarbonInterface  subRealQuarters(int|float $value = 1)                                              Sub quarters (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealQuarter()                                                                   Sub one quarter to the instance (using timestamp).
+ * @method        float            diffInUTCMonths(DateTimeInterface|string|null $date, bool $absolute = false)       Convert current and given date in UTC timezone and return a floating number of months.
+ * @method        CarbonInterface  addUTCQuarters(int|float $value = 1)                                               Add quarters (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCQuarter()                                                                    Add one quarter to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCQuarters(int|float $value = 1)                                               Sub quarters (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCQuarter()                                                                    Sub one quarter to the instance (using timestamp).
  * @method        CarbonPeriod     quartersUntil($endDate = null, int|float $factor = 1)                              Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each quarter or every X quarters if a factor is given.
- * @method        CarbonInterface  addRealYears(int|float $value = 1)                                                 Add years (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealYear()                                                                      Add one year to the instance (using timestamp).
- * @method        CarbonInterface  subRealYears(int|float $value = 1)                                                 Sub years (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealYear()                                                                      Sub one year to the instance (using timestamp).
+ * @method        float            diffInUTCQuarters(DateTimeInterface|string|null $date, bool $absolute = false)     Convert current and given date in UTC timezone and return a floating number of quarters.
+ * @method        CarbonInterface  addUTCYears(int|float $value = 1)                                                  Add years (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCYear()                                                                       Add one year to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCYears(int|float $value = 1)                                                  Sub years (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCYear()                                                                       Sub one year to the instance (using timestamp).
  * @method        CarbonPeriod     yearsUntil($endDate = null, int|float $factor = 1)                                 Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each year or every X years if a factor is given.
- * @method        CarbonInterface  addRealDecades(int|float $value = 1)                                               Add decades (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealDecade()                                                                    Add one decade to the instance (using timestamp).
- * @method        CarbonInterface  subRealDecades(int|float $value = 1)                                               Sub decades (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealDecade()                                                                    Sub one decade to the instance (using timestamp).
+ * @method        float            diffInUTCYears(DateTimeInterface|string|null $date, bool $absolute = false)        Convert current and given date in UTC timezone and return a floating number of years.
+ * @method        CarbonInterface  addUTCDecades(int|float $value = 1)                                                Add decades (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCDecade()                                                                     Add one decade to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCDecades(int|float $value = 1)                                                Sub decades (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCDecade()                                                                     Sub one decade to the instance (using timestamp).
  * @method        CarbonPeriod     decadesUntil($endDate = null, int|float $factor = 1)                               Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each decade or every X decades if a factor is given.
- * @method        CarbonInterface  addRealCenturies(int|float $value = 1)                                             Add centuries (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealCentury()                                                                   Add one century to the instance (using timestamp).
- * @method        CarbonInterface  subRealCenturies(int|float $value = 1)                                             Sub centuries (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealCentury()                                                                   Sub one century to the instance (using timestamp).
+ * @method        float            diffInUTCDecades(DateTimeInterface|string|null $date, bool $absolute = false)      Convert current and given date in UTC timezone and return a floating number of decades.
+ * @method        CarbonInterface  addUTCCenturies(int|float $value = 1)                                              Add centuries (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCCentury()                                                                    Add one century to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCCenturies(int|float $value = 1)                                              Sub centuries (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCCentury()                                                                    Sub one century to the instance (using timestamp).
  * @method        CarbonPeriod     centuriesUntil($endDate = null, int|float $factor = 1)                             Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each century or every X centuries if a factor is given.
- * @method        CarbonInterface  addRealMillennia(int|float $value = 1)                                             Add millennia (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMillennium()                                                                Add one millennium to the instance (using timestamp).
- * @method        CarbonInterface  subRealMillennia(int|float $value = 1)                                             Sub millennia (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMillennium()                                                                Sub one millennium to the instance (using timestamp).
+ * @method        float            diffInUTCCenturies(DateTimeInterface|string|null $date, bool $absolute = false)    Convert current and given date in UTC timezone and return a floating number of centuries.
+ * @method        CarbonInterface  addUTCMillennia(int|float $value = 1)                                              Add millennia (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMillennium()                                                                 Add one millennium to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMillennia(int|float $value = 1)                                              Sub millennia (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMillennium()                                                                 Sub one millennium to the instance (using timestamp).
  * @method        CarbonPeriod     millenniaUntil($endDate = null, int|float $factor = 1)                             Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each millennium or every X millennia if a factor is given.
+ * @method        float            diffInUTCMillennia(DateTimeInterface|string|null $date, bool $absolute = false)    Convert current and given date in UTC timezone and return a floating number of millennia.
  * @method        CarbonInterface  roundYear(float $precision = 1, string $function = "round")                        Round the current instance year with given precision using the given function.
  * @method        CarbonInterface  roundYears(float $precision = 1, string $function = "round")                       Round the current instance year with given precision using the given function.
  * @method        CarbonInterface  floorYear(float $precision = 1)                                                    Truncate the current instance year with given precision.
@@ -1075,6 +1090,8 @@ public function __toString();
     public function add($unit, $value = 1, ?bool $overflow = null): static;
 
     /**
+     * @deprecated Prefer to use add addUTCUnit() which more accurately defines what it's doing.
+     *
      * Add seconds to the instance using timestamp. Positive $value travels
      * forward while negative $value travels into the past.
      *
@@ -1085,6 +1102,17 @@ public function add($unit, $value = 1, ?bool $overflow = null): static;
      */
     public function addRealUnit(string $unit, $value = 1): static;
 
+    /**
+     * Add seconds to the instance using timestamp. Positive $value travels
+     * forward while negative $value travels into the past.
+     *
+     * @param string         $unit
+     * @param int|float|null $value
+     *
+     * @return static
+     */
+    public function addUTCUnit(string $unit, $value = 1): static;
+
     /**
      * Add given units to the current instance.
      */
@@ -4012,6 +4040,8 @@ public function startOfYear();
     public function sub($unit, $value = 1, ?bool $overflow = null): static;
 
     /**
+     * @deprecated Prefer to use add subUTCUnit() which more accurately defines what it's doing.
+     *
      * Subtract seconds to the instance using timestamp. Positive $value travels
      * into the past while negative $value travels forward.
      *
@@ -4022,6 +4052,17 @@ public function sub($unit, $value = 1, ?bool $overflow = null): static;
      */
     public function subRealUnit($unit, $value = 1): static;
 
+    /**
+     * Subtract seconds to the instance using timestamp. Positive $value travels
+     * into the past while negative $value travels forward.
+     *
+     * @param string $unit
+     * @param int    $value
+     *
+     * @return static
+     */
+    public function subUTCUnit($unit, $value = 1): static;
+
     /**
      * Subtract given units to the current instance.
      */
diff --git a/src/Carbon/Traits/Date.php b/src/Carbon/Traits/Date.php
index 6738ace519..fdf06ca105 100644
--- a/src/Carbon/Traits/Date.php
+++ b/src/Carbon/Traits/Date.php
@@ -533,81 +533,96 @@
  * @method        CarbonInterface  addWeekday()                                                                       Add one weekday to the instance (using date interval).
  * @method        CarbonInterface  subWeekdays(int|float $value = 1)                                                  Sub weekdays (the $value count passed in) to the instance (using date interval).
  * @method        CarbonInterface  subWeekday()                                                                       Sub one weekday to the instance (using date interval).
- * @method        CarbonInterface  addRealMicros(int|float $value = 1)                                                Add microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMicro()                                                                     Add one microsecond to the instance (using timestamp).
- * @method        CarbonInterface  subRealMicros(int|float $value = 1)                                                Sub microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMicro()                                                                     Sub one microsecond to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMicros(int|float $value = 1)                                                 Add microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMicro()                                                                      Add one microsecond to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMicros(int|float $value = 1)                                                 Sub microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMicro()                                                                      Sub one microsecond to the instance (using timestamp).
  * @method        CarbonPeriod     microsUntil($endDate = null, int|float $factor = 1)                                Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each microsecond or every X microseconds if a factor is given.
- * @method        CarbonInterface  addRealMicroseconds(int|float $value = 1)                                          Add microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMicrosecond()                                                               Add one microsecond to the instance (using timestamp).
- * @method        CarbonInterface  subRealMicroseconds(int|float $value = 1)                                          Sub microseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMicrosecond()                                                               Sub one microsecond to the instance (using timestamp).
+ * @method        float            diffInUTCMicros(DateTimeInterface|string|null $date, bool $absolute = false)       Convert current and given date in UTC timezone and return a floating number of microseconds.
+ * @method        CarbonInterface  addUTCMicroseconds(int|float $value = 1)                                           Add microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMicrosecond()                                                                Add one microsecond to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMicroseconds(int|float $value = 1)                                           Sub microseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMicrosecond()                                                                Sub one microsecond to the instance (using timestamp).
  * @method        CarbonPeriod     microsecondsUntil($endDate = null, int|float $factor = 1)                          Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each microsecond or every X microseconds if a factor is given.
- * @method        CarbonInterface  addRealMillis(int|float $value = 1)                                                Add milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMilli()                                                                     Add one millisecond to the instance (using timestamp).
- * @method        CarbonInterface  subRealMillis(int|float $value = 1)                                                Sub milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMilli()                                                                     Sub one millisecond to the instance (using timestamp).
+ * @method        float            diffInUTCMicroseconds(DateTimeInterface|string|null $date, bool $absolute = false) Convert current and given date in UTC timezone and return a floating number of microseconds.
+ * @method        CarbonInterface  addUTCMillis(int|float $value = 1)                                                 Add milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMilli()                                                                      Add one millisecond to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMillis(int|float $value = 1)                                                 Sub milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMilli()                                                                      Sub one millisecond to the instance (using timestamp).
  * @method        CarbonPeriod     millisUntil($endDate = null, int|float $factor = 1)                                Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each millisecond or every X milliseconds if a factor is given.
- * @method        CarbonInterface  addRealMilliseconds(int|float $value = 1)                                          Add milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMillisecond()                                                               Add one millisecond to the instance (using timestamp).
- * @method        CarbonInterface  subRealMilliseconds(int|float $value = 1)                                          Sub milliseconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMillisecond()                                                               Sub one millisecond to the instance (using timestamp).
+ * @method        float            diffInUTCMillis(DateTimeInterface|string|null $date, bool $absolute = false)       Convert current and given date in UTC timezone and return a floating number of milliseconds.
+ * @method        CarbonInterface  addUTCMilliseconds(int|float $value = 1)                                           Add milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMillisecond()                                                                Add one millisecond to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMilliseconds(int|float $value = 1)                                           Sub milliseconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMillisecond()                                                                Sub one millisecond to the instance (using timestamp).
  * @method        CarbonPeriod     millisecondsUntil($endDate = null, int|float $factor = 1)                          Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each millisecond or every X milliseconds if a factor is given.
- * @method        CarbonInterface  addRealSeconds(int|float $value = 1)                                               Add seconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealSecond()                                                                    Add one second to the instance (using timestamp).
- * @method        CarbonInterface  subRealSeconds(int|float $value = 1)                                               Sub seconds (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealSecond()                                                                    Sub one second to the instance (using timestamp).
+ * @method        float            diffInUTCMilliseconds(DateTimeInterface|string|null $date, bool $absolute = false) Convert current and given date in UTC timezone and return a floating number of milliseconds.
+ * @method        CarbonInterface  addUTCSeconds(int|float $value = 1)                                                Add seconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCSecond()                                                                     Add one second to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCSeconds(int|float $value = 1)                                                Sub seconds (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCSecond()                                                                     Sub one second to the instance (using timestamp).
  * @method        CarbonPeriod     secondsUntil($endDate = null, int|float $factor = 1)                               Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each second or every X seconds if a factor is given.
- * @method        CarbonInterface  addRealMinutes(int|float $value = 1)                                               Add minutes (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMinute()                                                                    Add one minute to the instance (using timestamp).
- * @method        CarbonInterface  subRealMinutes(int|float $value = 1)                                               Sub minutes (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMinute()                                                                    Sub one minute to the instance (using timestamp).
+ * @method        float            diffInUTCSeconds(DateTimeInterface|string|null $date, bool $absolute = false)      Convert current and given date in UTC timezone and return a floating number of seconds.
+ * @method        CarbonInterface  addUTCMinutes(int|float $value = 1)                                                Add minutes (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMinute()                                                                     Add one minute to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMinutes(int|float $value = 1)                                                Sub minutes (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMinute()                                                                     Sub one minute to the instance (using timestamp).
  * @method        CarbonPeriod     minutesUntil($endDate = null, int|float $factor = 1)                               Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each minute or every X minutes if a factor is given.
- * @method        CarbonInterface  addRealHours(int|float $value = 1)                                                 Add hours (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealHour()                                                                      Add one hour to the instance (using timestamp).
- * @method        CarbonInterface  subRealHours(int|float $value = 1)                                                 Sub hours (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealHour()                                                                      Sub one hour to the instance (using timestamp).
+ * @method        float            diffInUTCMinutes(DateTimeInterface|string|null $date, bool $absolute = false)      Convert current and given date in UTC timezone and return a floating number of minutes.
+ * @method        CarbonInterface  addUTCHours(int|float $value = 1)                                                  Add hours (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCHour()                                                                       Add one hour to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCHours(int|float $value = 1)                                                  Sub hours (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCHour()                                                                       Sub one hour to the instance (using timestamp).
  * @method        CarbonPeriod     hoursUntil($endDate = null, int|float $factor = 1)                                 Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each hour or every X hours if a factor is given.
- * @method        CarbonInterface  addRealDays(int|float $value = 1)                                                  Add days (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealDay()                                                                       Add one day to the instance (using timestamp).
- * @method        CarbonInterface  subRealDays(int|float $value = 1)                                                  Sub days (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealDay()                                                                       Sub one day to the instance (using timestamp).
+ * @method        float            diffInUTCHours(DateTimeInterface|string|null $date, bool $absolute = false)        Convert current and given date in UTC timezone and return a floating number of hours.
+ * @method        CarbonInterface  addUTCDays(int|float $value = 1)                                                   Add days (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCDay()                                                                        Add one day to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCDays(int|float $value = 1)                                                   Sub days (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCDay()                                                                        Sub one day to the instance (using timestamp).
  * @method        CarbonPeriod     daysUntil($endDate = null, int|float $factor = 1)                                  Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each day or every X days if a factor is given.
- * @method        CarbonInterface  addRealWeeks(int|float $value = 1)                                                 Add weeks (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealWeek()                                                                      Add one week to the instance (using timestamp).
- * @method        CarbonInterface  subRealWeeks(int|float $value = 1)                                                 Sub weeks (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealWeek()                                                                      Sub one week to the instance (using timestamp).
+ * @method        float            diffInUTCDays(DateTimeInterface|string|null $date, bool $absolute = false)         Convert current and given date in UTC timezone and return a floating number of days.
+ * @method        CarbonInterface  addUTCWeeks(int|float $value = 1)                                                  Add weeks (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCWeek()                                                                       Add one week to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCWeeks(int|float $value = 1)                                                  Sub weeks (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCWeek()                                                                       Sub one week to the instance (using timestamp).
  * @method        CarbonPeriod     weeksUntil($endDate = null, int|float $factor = 1)                                 Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each week or every X weeks if a factor is given.
- * @method        CarbonInterface  addRealMonths(int|float $value = 1)                                                Add months (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMonth()                                                                     Add one month to the instance (using timestamp).
- * @method        CarbonInterface  subRealMonths(int|float $value = 1)                                                Sub months (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMonth()                                                                     Sub one month to the instance (using timestamp).
+ * @method        float            diffInUTCWeeks(DateTimeInterface|string|null $date, bool $absolute = false)        Convert current and given date in UTC timezone and return a floating number of weeks.
+ * @method        CarbonInterface  addUTCMonths(int|float $value = 1)                                                 Add months (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMonth()                                                                      Add one month to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMonths(int|float $value = 1)                                                 Sub months (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMonth()                                                                      Sub one month to the instance (using timestamp).
  * @method        CarbonPeriod     monthsUntil($endDate = null, int|float $factor = 1)                                Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each month or every X months if a factor is given.
- * @method        CarbonInterface  addRealQuarters(int|float $value = 1)                                              Add quarters (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealQuarter()                                                                   Add one quarter to the instance (using timestamp).
- * @method        CarbonInterface  subRealQuarters(int|float $value = 1)                                              Sub quarters (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealQuarter()                                                                   Sub one quarter to the instance (using timestamp).
+ * @method        float            diffInUTCMonths(DateTimeInterface|string|null $date, bool $absolute = false)       Convert current and given date in UTC timezone and return a floating number of months.
+ * @method        CarbonInterface  addUTCQuarters(int|float $value = 1)                                               Add quarters (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCQuarter()                                                                    Add one quarter to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCQuarters(int|float $value = 1)                                               Sub quarters (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCQuarter()                                                                    Sub one quarter to the instance (using timestamp).
  * @method        CarbonPeriod     quartersUntil($endDate = null, int|float $factor = 1)                              Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each quarter or every X quarters if a factor is given.
- * @method        CarbonInterface  addRealYears(int|float $value = 1)                                                 Add years (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealYear()                                                                      Add one year to the instance (using timestamp).
- * @method        CarbonInterface  subRealYears(int|float $value = 1)                                                 Sub years (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealYear()                                                                      Sub one year to the instance (using timestamp).
+ * @method        float            diffInUTCQuarters(DateTimeInterface|string|null $date, bool $absolute = false)     Convert current and given date in UTC timezone and return a floating number of quarters.
+ * @method        CarbonInterface  addUTCYears(int|float $value = 1)                                                  Add years (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCYear()                                                                       Add one year to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCYears(int|float $value = 1)                                                  Sub years (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCYear()                                                                       Sub one year to the instance (using timestamp).
  * @method        CarbonPeriod     yearsUntil($endDate = null, int|float $factor = 1)                                 Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each year or every X years if a factor is given.
- * @method        CarbonInterface  addRealDecades(int|float $value = 1)                                               Add decades (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealDecade()                                                                    Add one decade to the instance (using timestamp).
- * @method        CarbonInterface  subRealDecades(int|float $value = 1)                                               Sub decades (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealDecade()                                                                    Sub one decade to the instance (using timestamp).
+ * @method        float            diffInUTCYears(DateTimeInterface|string|null $date, bool $absolute = false)        Convert current and given date in UTC timezone and return a floating number of years.
+ * @method        CarbonInterface  addUTCDecades(int|float $value = 1)                                                Add decades (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCDecade()                                                                     Add one decade to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCDecades(int|float $value = 1)                                                Sub decades (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCDecade()                                                                     Sub one decade to the instance (using timestamp).
  * @method        CarbonPeriod     decadesUntil($endDate = null, int|float $factor = 1)                               Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each decade or every X decades if a factor is given.
- * @method        CarbonInterface  addRealCenturies(int|float $value = 1)                                             Add centuries (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealCentury()                                                                   Add one century to the instance (using timestamp).
- * @method        CarbonInterface  subRealCenturies(int|float $value = 1)                                             Sub centuries (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealCentury()                                                                   Sub one century to the instance (using timestamp).
+ * @method        float            diffInUTCDecades(DateTimeInterface|string|null $date, bool $absolute = false)      Convert current and given date in UTC timezone and return a floating number of decades.
+ * @method        CarbonInterface  addUTCCenturies(int|float $value = 1)                                              Add centuries (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCCentury()                                                                    Add one century to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCCenturies(int|float $value = 1)                                              Sub centuries (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCCentury()                                                                    Sub one century to the instance (using timestamp).
  * @method        CarbonPeriod     centuriesUntil($endDate = null, int|float $factor = 1)                             Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each century or every X centuries if a factor is given.
- * @method        CarbonInterface  addRealMillennia(int|float $value = 1)                                             Add millennia (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  addRealMillennium()                                                                Add one millennium to the instance (using timestamp).
- * @method        CarbonInterface  subRealMillennia(int|float $value = 1)                                             Sub millennia (the $value count passed in) to the instance (using timestamp).
- * @method        CarbonInterface  subRealMillennium()                                                                Sub one millennium to the instance (using timestamp).
+ * @method        float            diffInUTCCenturies(DateTimeInterface|string|null $date, bool $absolute = false)    Convert current and given date in UTC timezone and return a floating number of centuries.
+ * @method        CarbonInterface  addUTCMillennia(int|float $value = 1)                                              Add millennia (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  addUTCMillennium()                                                                 Add one millennium to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMillennia(int|float $value = 1)                                              Sub millennia (the $value count passed in) to the instance (using timestamp).
+ * @method        CarbonInterface  subUTCMillennium()                                                                 Sub one millennium to the instance (using timestamp).
  * @method        CarbonPeriod     millenniaUntil($endDate = null, int|float $factor = 1)                             Return an iterable period from current date to given end (string, DateTime or Carbon instance) for each millennium or every X millennia if a factor is given.
+ * @method        float            diffInUTCMillennia(DateTimeInterface|string|null $date, bool $absolute = false)    Convert current and given date in UTC timezone and return a floating number of millennia.
  * @method        CarbonInterface  roundYear(float $precision = 1, string $function = "round")                        Round the current instance year with given precision using the given function.
  * @method        CarbonInterface  roundYears(float $precision = 1, string $function = "round")                       Round the current instance year with given precision using the given function.
  * @method        CarbonInterface  floorYear(float $precision = 1)                                                    Truncate the current instance year with given precision.
@@ -2704,9 +2719,10 @@ public function __call(string $method, array $parameters): mixed
 
         if ($action === 'add' || $action === 'sub') {
             $unit = substr($unit, 3);
+            $utcUnit = $this->getUTCUnit($unit);
 
-            if (str_starts_with($unit, 'Real')) {
-                $unit = static::singularUnit(substr($unit, 4));
+            if ($utcUnit) {
+                $unit = static::singularUnit($utcUnit);
 
                 return $this->{"{$action}RealUnit"}($unit, ...$parameters);
             }
@@ -2928,4 +2944,17 @@ private function callGetOrSet(string $name, mixed $value): mixed
 
         return $this->get($name);
     }
+
+    private function getUTCUnit(string $unit): ?string
+    {
+        if (str_starts_with($unit, 'Real')) {
+            return substr($unit, 4);
+        }
+
+        if (str_starts_with($unit, 'UTC')) {
+            return substr($unit, 3);
+        }
+
+        return null;
+    }
 }
diff --git a/tests/Carbon/IsTest.php b/tests/Carbon/IsTest.php
index edf1f7ec36..cc57d7b70b 100644
--- a/tests/Carbon/IsTest.php
+++ b/tests/Carbon/IsTest.php
@@ -17,7 +17,6 @@
 use Carbon\Carbon;
 use DateTime;
 use PHPUnit\Framework\Attributes\DataProvider;
-use PHPUnit\Framework\Attributes\Group;
 use stdClass;
 use Tests\AbstractTestCase;
 use TypeError;
@@ -610,7 +609,6 @@ public function testIsCurrentSecondFalse()
         $this->assertFalse(Carbon::now()->subDay()->isCurrentSecond());
     }
 
-    #[Group('php-8.1')]
     public function testIsSameMicrosecond()
     {
         $current = new Carbon('2018-05-06T13:30:54.123456');
diff --git a/tests/Carbon/ModifyTest.php b/tests/Carbon/ModifyTest.php
index 9e09e47119..ba5d8403f3 100644
--- a/tests/Carbon/ModifyTest.php
+++ b/tests/Carbon/ModifyTest.php
@@ -18,7 +18,6 @@
 use Closure;
 use DateMalformedStringException;
 use InvalidArgumentException;
-use PHPUnit\Framework\Attributes\Group;
 use Tests\AbstractTestCase;
 
 class ModifyTest extends AbstractTestCase
@@ -31,7 +30,6 @@ public function testSimpleModify()
         $this->assertSame(24.0, $a->diffInHours($b));
     }
 
-    #[Group('php-8.1')]
     public function testTimezoneModify()
     {
         $php81Fix = 1.0;
@@ -50,7 +48,7 @@ public function testTimezoneModify()
 
         $a = new Carbon('2014-03-30 00:00:00', 'Europe/London');
         $b = $a->copy();
-        $b->addRealHours(24);
+        $b->addUTCHours(24);
         $this->assertSame(-24.0, $b->diffInHours($a, false));
         $this->assertSame(-24.0 * 60, $b->diffInMinutes($a, false));
         $this->assertSame(-24.0 * 60 * 60, $b->diffInSeconds($a, false));
@@ -117,6 +115,15 @@ public function testTimezoneModify()
         $this->assertSame(-24.0 * 60 * 60 * 1000, $b->diffInMilliseconds($a, false));
         $this->assertSame(-24.0 * 60 * 60 * 1000000, $b->diffInMicroseconds($a, false));
 
+        $a = new Carbon('2014-03-30 00:00:00', 'Europe/London');
+        $b = $a->copy();
+        $b->addUTCDay();
+        $this->assertSame(-24.0, $b->diffInHours($a, false));
+        $this->assertSame(-24.0 * 60, $b->diffInMinutes($a, false));
+        $this->assertSame(-24.0 * 60 * 60, $b->diffInSeconds($a, false));
+        $this->assertSame(-24.0 * 60 * 60 * 1000, $b->diffInMilliseconds($a, false));
+        $this->assertSame(-24.0 * 60 * 60 * 1000000, $b->diffInMicroseconds($a, false));
+
         $a = new Carbon('2014-03-30 00:00:00', 'Europe/London');
         $b = $a->copy();
         $b->addRealWeeks(1 / 7);
diff --git a/tests/CarbonImmutable/IsTest.php b/tests/CarbonImmutable/IsTest.php
index 4d6ae185c2..9177548558 100644
--- a/tests/CarbonImmutable/IsTest.php
+++ b/tests/CarbonImmutable/IsTest.php
@@ -17,7 +17,6 @@
 use DateTime;
 use InvalidArgumentException;
 use PHPUnit\Framework\Attributes\DataProvider;
-use PHPUnit\Framework\Attributes\Group;
 use stdClass;
 use Tests\AbstractTestCase;
 use TypeError;
@@ -640,7 +639,6 @@ public function testIsCurrentSecondFalse()
         $this->assertFalse(Carbon::now()->subDay()->isCurrentSecond());
     }
 
-    #[Group('php-8.1')]
     public function testIsSameMicrosecond()
     {
         $current = new Carbon('2018-05-06T13:30:54.123456');
diff --git a/tests/CarbonImmutable/ModifyTest.php b/tests/CarbonImmutable/ModifyTest.php
index 4ee081b816..b6dd4ebc01 100644
--- a/tests/CarbonImmutable/ModifyTest.php
+++ b/tests/CarbonImmutable/ModifyTest.php
@@ -14,7 +14,6 @@
 namespace Tests\CarbonImmutable;
 
 use Carbon\CarbonImmutable as Carbon;
-use PHPUnit\Framework\Attributes\Group;
 use Tests\AbstractTestCase;
 
 class ModifyTest extends AbstractTestCase
@@ -33,7 +32,6 @@ public function testSimpleModifyWithNamedParameter()
         $this->assertSame(24.0, $a->diffInHours($b));
     }
 
-    #[Group('php-8.1')]
     public function testTimezoneModify()
     {
         $php81Fix = 1.0;
diff --git a/tests/CarbonInterval/AddTest.php b/tests/CarbonInterval/AddTest.php
index 3a25291da6..071a5989a3 100644
--- a/tests/CarbonInterval/AddTest.php
+++ b/tests/CarbonInterval/AddTest.php
@@ -20,7 +20,6 @@
 use DateTime;
 use DateTimeImmutable;
 use InvalidArgumentException;
-use PHPUnit\Framework\Attributes\Group;
 use PHPUnit\Framework\Attributes\TestWith;
 use Tests\AbstractTestCase;
 use Tests\Carbon\Fixtures\MyCarbon;
@@ -77,7 +76,6 @@ public function testAddWithNegativeDiffDateInterval()
         $this->assertCarbonInterval($ci, 4, 3, 28, 8, 10, 11);
     }
 
-    #[Group('php-8.1')]
     public function testAddMicroseconds()
     {
         $diff = Carbon::now()->diff(Carbon::now()->addDays(3)->addMicroseconds(111222));