adding a unit test

sdk/core/src/test/java/com/klaviyo/core/config/SystemClockTest.kt

@@ -1,10 +1,34 @@
 package com.klaviyo.core.config
 
+import java.text.SimpleDateFormat
+import java.util.Date
+import java.util.Locale
+import java.util.TimeZone
+import junit.framework.TestCase.assertEquals
+import org.junit.After
 import org.junit.Assert
+import org.junit.Before
 import org.junit.Test
 
 class SystemClockTest {
 
+    private var defaultLocale: Locale? = null
+
+    @Before
+    fun setUp() {
+        // Save the original default locale
+        defaultLocale = Locale.getDefault()
+
+        // Set default locale to Arabic
+        Locale.setDefault(Locale("ar"))
+    }
+
+    @After
+    fun tearDown() {
+        // Restore the original default locale after test
+        defaultLocale?.let { Locale.setDefault(it) }
+    }
+
     @Test
     fun `Clock uses proper date format`() {
         val regex7 = "^\\d{4}(-\\d\\d(-\\d\\d(T\\d\\d:\\d\\d(:\\d\\d)?(\\.\\d+)?(([+-]\\d\\d:*\\d\\d)|Z)?)?)?)?\$".toRegex()
@@ -36,4 +60,20 @@ class SystemClockTest {
         Thread.sleep(20L)
         Assert.assertEquals(1, counter)
     }
+
+    @Test
+    fun `Clock uses English locale for date formatting`() {
+        val expectedFormat = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ", Locale.ENGLISH).apply {
+            timeZone = TimeZone.getTimeZone("UTC")
+        }
+
+        // Use a known timestamp for test consistency
+        val testTimestamp = 0L
+        val expectedOutput = expectedFormat.format(Date(testTimestamp))
+
+        // using the utility
+        val actualOutput = SystemClock.isoTime(testTimestamp)
+
+        assertEquals(expectedOutput, actualOutput)
+    }
 }