Time zones: Locale behavior
Defines user-visible formatting, language selection, fallback, content behavior, and regional edge cases for time zones. It fixes adoption boundaries and observable failure evidence while keeping environment-specific limits configurable.
Package status: reference context ready for human review. The contract and test scenarios are complete, but no claim is made that an adopting implementation has passed them.
Decision
For Time zones, adopt canonical locale-neutral data plus explicit presentation locale. Define a deterministic user journey with visible state, reversible choices where possible, preserved input, and accessible recovery. This package is a reference contract: the adopting team must choose numeric limits, providers, jurisdictions, and operational owners from evidence in its own environment.
Scope
- The Time zones actors, inputs, outputs, states, policy or schema versions, and externally visible outcomes described by this ux block.
- Primary and alternate interfaces, background work, caches, integrations, support paths, and evidence that can exercise the same boundary.
- Adoption-specific configuration, rollout, recovery, and verification responsibilities needed to apply the reference safely.
Outside this block
- Choosing a universal vendor, framework, jurisdiction, numeric threshold, retention period, or service-level objective for every adopter.
- Claiming that packaged scenarios have run against a downstream implementation or that this reference grants legal, security, or accessibility certification.
Contract
- Persist canonical values and stable translation keys; apply locale-specific formatting only at presentation or document-generation boundaries.
- Resolve requested, user, organization, and product fallback locales through one deterministic, observable chain.
- Use language tags and locale data from maintained standards; do not infer language, region, currency, or legal terms from one another.
- Test expansion, plural categories, bidirectional text, missing resources, time zones, currencies, and non-Latin input with representative fixtures.
- Show progress only while work is actually pending and prevent duplicate activation without hiding the user's committed intent.
- Use plain, action-specific messages that distinguish validation, permission, connectivity, conflict, and terminal failure.
- Store instants in a universal timeline and retain the relevant IANA zone and original local intent wherever scheduling, recurrence, or legal interpretation depends on it.
- Define daylight-saving gaps and overlaps, zone changes, historical rule updates, display locale, cutoffs, and comparison semantics and never substitute a fixed offset for a zone.
Implementation guidance
- Prototype the longest, empty, slow, offline, denied, and assistive-technology paths before locking the happy-path layout.
- Model Time zones inputs, outputs, actors, states, invariants, side effects, and evidence before selecting framework or vendor details.
- Store the applicable Time zones contract or policy version with material state so migrations, replay, and support decisions remain attributable.
- Introduce the path behind controlled rollout, compare expected and observed outcomes, and keep a tested recovery route until adoption evidence is complete.
Failure handling and safeguards
- A missing or invalid resource follows the declared fallback chain, records the key and locale safely, and never exposes an internal identifier as final copy.
- Invalid or contradictory Time zones state is rejected or quarantined; the implementation never guesses a value that broadens authority or duplicates an effect.
- Retries are bounded and use durable identity; after exhaustion, work reaches an inspectable terminal state with an accountable owner.
Verification and operations
- Complete the journey with keyboard, touch, screen reader, narrow viewport, delayed network, and a recoverable server error.
- Monitor Time zones success, denial, validation failure, dependency failure, retry exhaustion, and recovery by contract version without sensitive payload dimensions.
- Re-run paired positive and negative fixtures after policy, schema, dependency, migration, or boundary changes and preserve the resulting evidence.
Adoption assumptions
- Names and values in the example are a concrete fixture, not universal defaults; adopters replace them through documented evidence and ownership.
- The adopting system can provide authenticated identity, durable operation or record versions, bounded telemetry, and a controlled path for change.
The executable-looking examples in this package are fixtures and acceptance contracts. Run the collection validator to check structure and metadata, then translate and execute the scenarios in the target repository before recording implementation evidence.