Aglet

Verify Timezone and Timestamp Handling at Boundaries

Timezone verification checks both storage fidelity and business-facing grouping. Exercise explicit instants at every relevant boundary, compare filters and aggregates, and inspect display values separately. A test that passes in one offset or season does not establish correct behavior for all local dates.

Check whether the outcome improved

  1. Assert instant preservation

    Round-trip timestamps with positive and negative offsets, fractional precision, and zone transitions. Confirm the stored or normalized instant represents the same event and that missing offsets produce the documented outcome. Include malformed and date-only inputs so fallback behavior is visible.

  2. Assert window membership

    Run daily, monthly, and cutoff queries against fixtures just outside and inside each boundary. Compare included identifiers and totals with the declared business zone. Review the first and last event in every window, since aggregate equality can hide a pair of swapped records.

  3. Check rendered and exported dates

    Verify the displayed date, sort order, and exported representation use the intended zone and precision. Compare a known instant across contexts without relying on a machine-local default. Retain the fixture expectations and note untested historical zones or calendar policies.

What to carry forward

Accept timezone handling when instants round-trip, boundary membership matches the declared zone, ordering is stable, and display or export semantics are explicit. Keep verification open for unsupported offsets, daylight-saving rules, or policy decisions. Report the exact zone and date range covered by the checks.

Keep the decision with the work.

Use a Work Item in Aglet to record the problem, the evidence you have, and the next decision. Add an owner and priority, then keep updates in the discussion so the next person can follow the reasoning.

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