fix: handle timezone correctly when DJANGO_CELERY_BEAT_TZ_AWARE=False (Issue #924)

django_celery_beat/schedulers.py

@@ -12,13 +12,14 @@
 from celery import current_app, schedules
 from celery.beat import ScheduleEntry, Scheduler
 from celery.utils.log import get_logger
-from celery.utils.time import maybe_make_aware
+from celery.utils.time import is_naive, make_aware
 from django.conf import settings
 from django.core.exceptions import ObjectDoesNotExist
 from django.db import close_old_connections, transaction
 from django.db.models import Case, F, IntegerField, Q, When
 from django.db.models.functions import Cast
 from django.db.utils import DatabaseError, InterfaceError
+from django.utils import timezone
 from kombu.utils.encoding import safe_repr, safe_str
 from kombu.utils.json import dumps, loads
 
@@ -117,8 +118,6 @@ def is_due(self):
         # START DATE: only run after the `start_time`, if one exists.
         if self.model.start_time is not None:
             now = self._default_now()
-            if getattr(settings, 'DJANGO_CELERY_BEAT_TZ_AWARE', True):
-                now = maybe_make_aware(self._default_now())
             if now < self.model.start_time:
                 # The datetime is before the start date - don't run.
                 # send a delay to retry on start_time
@@ -147,20 +146,27 @@ def is_due(self):
             # Don't recheck
             return schedules.schedstate(False, NEVER_CHECK_TIMEOUT)
 
-        # CAUTION: make_aware assumes settings.TIME_ZONE for naive datetimes,
-        # while maybe_make_aware assumes utc for naive datetimes
-        tz = self.app.timezone
-        last_run_at_in_tz = maybe_make_aware(self.last_run_at).astimezone(tz)
+        # Handle both naive and timezone-aware last_run_at properly
+        if is_naive(self.last_run_at):
+            # Naive datetime - make it aware using app timezone
+            last_run_at_in_tz = make_aware(self.last_run_at, self.app.timezone)
+        else:
+            # Already timezone-aware - convert to app timezone if needed
+            last_run_at_in_tz = self.last_run_at.astimezone(self.app.timezone)
         return self.schedule.is_due(last_run_at_in_tz)
 
     def _default_now(self):
-        if getattr(settings, 'DJANGO_CELERY_BEAT_TZ_AWARE', True):
-            now = datetime.datetime.now(self.app.timezone)
-        else:
-            # this ends up getting passed to maybe_make_aware, which expects
-            # all naive datetime objects to be in utc time.
-            now = datetime.datetime.utcnow()
-        return now
+        now = timezone.now().astimezone(self.app.timezone)
+        tz_aware = (
+            getattr(settings, 'DJANGO_CELERY_BEAT_TZ_AWARE', True) and
+            getattr(settings, 'USE_TZ', True)
+        )
+        if tz_aware:
+            return now
+        # Return a naive datetime representing local time in the app's timezone.
+        # This path is taken when either DJANGO_CELERY_BEAT_TZ_AWARE or USE_TZ
+        # is set to False in Django settings (i.e., if either is False).
+        return now.replace(tzinfo=None)
 
     def __next__(self):
         self.model.last_run_at = self._default_now()

t/unit/test_schedulers.py

@@ -333,7 +333,7 @@ def test_entry_is_due__no_use_tz(self):
         assert self.app.timezone.key == 'Europe/Berlin'
 
         # simulate last_run_at from DB - not TZ aware but localtime
-        right_now = datetime.utcnow()
+        right_now = timezone.now().astimezone(self.app.timezone).replace(tzinfo=None)
 
         m = self.create_model_crontab(
             crontab(minute='*/10'),
@@ -364,7 +364,7 @@ def test_entry_and_model_last_run_at_with_utc_no_use_tz(self, monkeypatch):
             time.tzset()
         assert self.app.timezone.key == 'Europe/Berlin'
         # simulate last_run_at from DB - not TZ aware but localtime
-        right_now = datetime.utcnow()
+        right_now = timezone.now().astimezone(self.app.timezone).replace(tzinfo=None)
         # make sure to use fixed date time
         monkeypatch.setattr(self.Entry, '_default_now', lambda o: right_now)
         m = self.create_model_crontab(
@@ -398,7 +398,7 @@ def test_entry_and_model_last_run_at_when_model_changed(self, monkeypatch):
             time.tzset()
         assert self.app.timezone.key == 'Europe/Berlin'
         # simulate last_run_at from DB - not TZ aware but localtime
-        right_now = datetime.utcnow()
+        right_now = timezone.now().astimezone(self.app.timezone).replace(tzinfo=None)
         # make sure to use fixed date time
         monkeypatch.setattr(self.Entry, '_default_now', lambda o: right_now)
         m = self.create_model_crontab(
@@ -451,7 +451,7 @@ def test_entry_is_due__celery_timezone_doesnt_match_time_zone(self):
 
         # simulate last_run_at all none, doing the same thing that
         # _default_now() would do
-        right_now = datetime.utcnow()
+        right_now = timezone.now().astimezone(self.app.timezone).replace(tzinfo=None)
 
         m = self.create_model_crontab(
             crontab(minute='*/10'),