DJANGO_CELERY_BEAT_TZ_AWARE = False Time zone usage issue

[NeverStopDreamingWang]

I checked the solutions in celery/django-celery-beat/issues/798, specifically #798 (comment).

However, this still doesn't solve the problem.

Core Problem Statement

The root cause occurs when USE_TZ ≠ DJANGO_CELERY_BEAT_TZ_AWARE

This mismatch creates timezone awareness incompatibility between

leading to TypeError: can't compare offset-naive and offset-aware datetimes during time comparisons.

Key Conflict Points

Django's USE_TZ Behavior

Setting	Storage Behavior	Read Behavior
USE_TZ=True	Stores all times as UTC	Converts to UTC timezone when reading
USE_TZ=False	Stores timezone-naive times	Reads timezone-naive times

Celery Beat's DJANGO_CELERY_BEAT_TZ_AWARE Behavior

Setting	Time Generation Method
True	datetime.now(self.app.timezone) (timezone-aware)
False	datetime.utcnow() (timezone-naive UTC)

    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

Conflict Scenarios Analysis

Scenario	DJANGO_CELERY_BEAT_TZ_AWARE	USE_TZ	_default_now() Returns	ORM Returns	Result
1	True	False	Timezone-aware	Timezone-naive	Comparison error
2	False	True	Timezone-naive	Timezone-aware	Comparison error
3	True	True	Timezone-aware	Timezone-aware	Valid
4	False	False	Timezone-naive	Timezone-naive	Valid

Core Problems with last_run_at

When USE_TZ ≠ DJANGO_CELERY_BEAT_TZ_AWARE:

Celery Version: 5.5.1
Celery-Beat Version: 2.8.1

[auvipy]

would you mind come with the proposed fix with appropriate test cases?

[NeverStopDreamingWang]

Hi @auvipy, Thank you for your feedback! I've implemented a fix for this issue and created a pull request with comprehensive test cases. Here are the details: Pull Request: fix: handle timezone correctly when DJANGO_CELERY_BEAT_TZ_AWARE=False (Issue #924) #926 Test Coverage:  DJANGO_CELERY_BEAT_TZ_AWARE (True/False) USE_TZ (True/False) The changes: Fixed timezone handling in schedulers.py to ensure consistent behavior Added configuration validation warnings Updated documentation regarding timezone precedence I've verified the solution works in these scenarios: ✅ Existing tasks maintain backward compatibility ✅ New tasks respect all timezone configuration combinations ✅ No performance regression detected Please let me know if you'd like any adjustments to the implementation. I'm happy to iterate based on your feedback. Best regards, [NeverStopDreamingWang] [Optional: NeverStopDreamingWang] 最爱吃青菜 ***@***.*** 原始邮件 发件人：auvipy ***@***.***> 发件时间：2025年7月31日 12:20 收件人：celery/django-celery-beat ***@***.***> 抄送：最爱吃青菜 ***@***.***>, Author ***@***.***> 主题：Re: [celery/django-celery-beat] DJANGO_CELERY_BEAT_TZ_AWARE = FalseTime zone usage issue (Issue #924) auvipy left a comment (celery/django-celery-beat#924) would you mind come with the proposed fix with appropriate test cases? — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you authored the thread.

[auvipy]

the posposed change has no unit tests and also failing the current CI build

[NeverStopDreamingWang]

I forgot to modify the test cases.

[NeverStopDreamingWang]

I forgot to modify the test cases. Has been resubmitted 最爱吃青菜 ***@***.*** 原始邮件 发件人：auvipy ***@***.***> 发件时间：2025年7月31日 19:06 收件人：celery/django-celery-beat ***@***.***> 抄送：最爱吃青菜 ***@***.***>, Author ***@***.***> 主题：Re: [celery/django-celery-beat] DJANGO_CELERY_BEAT_TZ_AWARE = FalseTime zone usage issue (Issue #924) auvipy left a comment (celery/django-celery-beat#924) the posposed change has no unit tests and also failing the current CI build — Reply to this email directly, view it on GitHub, or unsubscribe. You are receiving this because you authored the thread.

[auvipy]

When USE_TZ ≠ DJANGO_CELERY_BEAT_TZ_AWARE: is this a suggested or ideal setup?

[NeverStopDreamingWang]

When USE_TZ ≠ DJANGO_CELERY_BEAT_TZ_AWARE: is this a suggested or ideal setup?

Regardless of whether having USE_TZ ≠ DJANGO_CELERY_BEAT_TZ_AWARE is considered ideal or not, I think the main concern should be the potential issues introduced by the USE_TZ setting itself.
You cannot force users to configure it to a specific value; instead, the goal should be to support all possible configurations as much as possible, while minimizing confusion for users.