Reject local times that do not identify one instant
A booking form submits 01:30 on a daylight-saving fallback day without an offset. Store an instant plus display zone and explicitly handle ambiguous or nonexistent local times.
- Focused work estimate
- 1h 45m + prerequisites
- Priority in the scenario
- High
- Engineering practice
- Time zones · Input validation · Temporal modeling
Estimated field mix
- Integrations60%
- Backend40%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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Project context
A fictional consultancy books appointments across time zones. The first connector duplicates events after timeouts and offers slots during stale calendar sync. Use a local calendar-provider double and synthetic calendars.
Setup prerequisites
- Create a local provider double for free/busy, event creation, updates, cancellation, and expiring tokens.
- Use synthetic calendars and an injected clock; no calendar account or outgoing invitation is required.
Preceding work
No earlier ticket is required. Complete the project setup above.
Acceptance criteria
- Bookings store UTC start/end instants and an IANA display-zone identifier.
- Nonexistent local times are rejected with a selectable valid alternative.
- Ambiguous local times require an explicit offset or occurrence choice and preserve that choice.
Implementation constraints
- Use established time-zone APIs or libraries; do not hard-code seasonal offsets.
Verification to include
- Test a normal date and both sides of a known spring gap and autumn overlap in a fixture zone.
- Submit an unknown zone and an end before start and verify validation errors without provider calls.
Deliverables
- Booking time contract and daylight-saving boundary cases
Rollout and recovery
Validate time inputs before availability or event creation; keep existing stored instants unchanged during migration.
Value of the work
For the engineer: Practice time modeling, conflict-safe booking, external state reconciliation, and credential lifecycle boundaries.
For the team: Review whether integration work protects appointment correctness and offers clear recovery when a provider is uncertain.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.