Adjust "when" value parsing to handle YYYY-MM-DD consistently

ISO-8601-like date formats shouldn't depend on system locale by default,
only localized formats like DD-MM-YYYY or MM-DD-YYYY.

gcalcli/cli.py

@@ -38,8 +38,8 @@
 from .gcal import GoogleCalendarInterface
 from .printer import Printer, valid_color_name
 from .validators import (
-    get_date_input_description,
     get_input,
+    DATE_INPUT_DESCRIPTION,
     PARSABLE_DATE,
     PARSABLE_DURATION,
     REMINDER,
@@ -116,12 +116,11 @@ def run_add_prompt(parsed_args, printer):
     if parsed_args.where is None:
         parsed_args.where = get_input(printer, 'Location: ', STR_ALLOW_EMPTY)
     if parsed_args.when is None:
-        date_format_desc = get_date_input_description()
         parsed_args.when = get_input(
             printer,
             'When (? for help): ',
             PARSABLE_DATE,
-            help=f'Expected format: {date_format_desc}',
+            help=f'Expected format: {DATE_INPUT_DESCRIPTION}',
         )
     if parsed_args.duration is None and parsed_args.end is None:
         if parsed_args.allday:

gcalcli/utils.py

@@ -93,7 +93,7 @@ def get_times_from_duration(
     return start.isoformat(), stop.isoformat()
 
 
-def is_dayfirst_locale():
+def _is_dayfirst_locale():
     """Detect whether system locale date format has day first.
 
     Examples:
@@ -121,10 +121,13 @@ def get_time_from_str(when):
         hour=0, minute=0, second=0, microsecond=0
     )
 
+    # Only apply dayfirst=True if date actually starts with "XX-XX-".
+    # Other forms like YYYY-MM-DD shouldn't rely on locale by default (#792).
+    kwargs = {}
+    if re.match(r'^\d{1,2}-\d{1,2}-', when):
+        kwargs['dayfirst'] = _is_dayfirst_locale()
     try:
-        event_time = dateutil_parse(
-            when, default=zero_oclock_today, dayfirst=is_dayfirst_locale()
-        )
+        event_time = dateutil_parse(when, default=zero_oclock_today, **kwargs)
     except ValueError:
         struct, result = fuzzy_date_parse(when)
         if not result:

gcalcli/validators.py

@@ -6,7 +6,6 @@
     get_time_from_str,
     get_timedelta_from_str,
     REMINDER_REGEX,
-    is_dayfirst_locale,
 )
 
 # TODO: in the future, pull these from the API
@@ -15,6 +14,10 @@
                          'banana', 'tangerine', 'peacock', 'graphite',
                          'blueberry', 'basil', 'tomato']
 
+DATE_INPUT_DESCRIPTION = '\
+a date (e.g. 2019-12-31, tomorrow 10am, 2nd Jan, Jan 4th, etc) or valid time \
+if today'
+
 
 def get_override_color_id(color):
     return str(VALID_OVERRIDE_COLORS.index(color) + 1)
@@ -68,13 +71,6 @@ def str_to_int_validator(input_str):
         )
 
 
-def get_date_input_description():
-    dayfirst = is_dayfirst_locale()
-    sample_date = '2019-31-12' if dayfirst else '2019-12-31'
-    return f'a date (e.g. {sample_date}, tomorrow 10am, 2nd Jan, Jan 4th, etc) \
-or valid time if today'
-
-
 def parsable_date_validator(input_str):
     """
     A filter allowing any string which can be parsed
@@ -85,9 +81,8 @@ def parsable_date_validator(input_str):
         get_time_from_str(input_str)
         return input_str
     except ValueError:
-        format_desc = get_date_input_description()
         raise ValidationError(
-            f'Expected format: {format_desc}. '
+            f'Expected format: {DATE_INPUT_DESCRIPTION}. '
             '(Ctrl-C to exit)\n'
         )