---
title: "Verify timezone changes preserve a scheduled instant"
description: "Check a sandbox event viewed after an account timezone change, separating the same real-world instant from its newly formatted local calendar time."
canonical_url: "https://vostride.com/agent-library/scheduling/timezone-change-keeps-event-instant.md"
md_url: "https://vostride.com/agent-library/scheduling/timezone-change-keeps-event-instant.md"
content_kind: "recipe"
topic: "scheduling"
---

# Verify timezone changes preserve a scheduled instant

Check a sandbox event viewed after an account timezone change, separating the same real-world instant from its newly formatted local calendar time.

## Risk

Changing a display preference must follow the product event semantics. For an instant-based event, a different local label is expected but a changed canonical start is a regression; keep floating events outside this fixture.

## Fixtures

- An owned sandbox calendar containing one explicitly instant-based event with a fixed canonical start and duration.
- Two account timezone settings whose prepared expected local dates differ, making midnight rollover observable.
- A disposable attendee and an independent event oracle that records canonical start, end, timezone metadata, and immutable identity.

## Steps

1. Open the event in the first timezone and verify its local date and time match the prepared mapping.
2. Change the account display timezone through product settings and verify the setting is saved.
3. Reopen the event and verify its local date and time now match the second mapping, including the expected date rollover.
4. Inspect the independent oracle and verify the event start, end, duration, and identifier are unchanged; check the calendar day view for one occurrence on the newly expected local date.

## Expected results

- The canonical event instant and duration do not change with display timezone.
- The new local label and calendar day match the independent mapping.
- The event appears exactly once without a duplicate on its previous display date.

## False-pass traps

- Using two zones with the same current offset does not exercise meaningful conversion.
- A floating all-day event follows a different contract and invalidates this instant-based expectation.

## Cleanup

- Restore the account timezone and remove the disposable event if created for this run.

## Use with agent-qa

Adapt this test design to your application's acceptance criteria and configured target using the [recipe execution guide](/agent-library/software-factory/turn-a-recipe-into-an-agent-qa-test.md). External fixture setup and non-UI checks require your own supported hooks or test tooling. Validate the authored test, execute it, and inspect the completed evidence; this recipe is not a recorded test result.

## References

- [agent-qa first test](/docs/agent-qa/guides/first-test.md)
- [agent-qa hooks](/docs/agent-qa/guides/hooks.md)
- [agent-qa test](/docs/agent-qa/configuration/test.md)

- [Scheduling and calendar QA recipes](/agent-library/scheduling.md)
- [Software factory QA library](/agent-library.md)