Timezone Review (Claude Code)

A Claude Code skill for scheduling, reporting, streaks, and expiry. Timezone bugs pass every test because the developer, the test machine, and CI are usually all on the same offset, then appear in production as complaints that sound impossible. The root cause is nearly always one thing: a calendar date and a true instant are different types and the code uses one where it means the other. Classifies every date field as instant, calendar date, or local wall time, finds where the server's own clock leaks into a result, locates every day boundary and asks whose midnight it is, and checks the arithmetic that assumes a day is always 86400 seconds.