python runtime_error ai_generated true

AssertionError: assert datetime.date(2025, 1, 1) == datetime.date(2024, 12, 31) # only fails in CI in UTC

ID: python/pytest-freezegun-timezone

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80%Fix Rate
82%Confidence
0Evidence
2025-09-19First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
1.5 active — — —

Root Cause

freezegun freezes UTC time by default; tests that assert on local time or use timezone-aware code fail when developer machine TZ differs from CI TZ.

generic

中文

freezegun 默认冻结 UTC 时间；断言本地时间或使用时区感知代码的测试在开发者机器 TZ 与 CI TZ 不同时失败。

Workarounds

  1. 90% success 
    from freezegun import freeze_time

@freeze_time('2025-01-01 00:00:00', tz_offset=0)
def test_x():
    ...

# or use tz-aware datetimes in assertions
  2. 88% success 
    from datetime import datetime, timezone

now = datetime.now(timezone.utc)
# assert against UTC-aware values in tests

Dead Ends

Common approaches that don't work:

  1. 85% fail

    Makes CI match freezegun but local runs diverge; the underlying timezone-aware bug remains.

  2. 90% fail

    freezegun interprets the string as UTC; local-time assertions still fail.

  3. 80% fail

    Tests become flaky around midnight and month boundaries; loses determinism.