# DateTime and time zones

**Test family:** `DTM`

- **DTM-001** Preserve the instant and intended zone separately where future local time matters.
- **DTM-002** Test UTC, positive/negative offsets, half/quarter-hour zones, and user/organization/object zones.
- **DTM-003** Test spring-forward nonexistent time and fall-back duplicated time with explicit resolution.
- **DTM-004** Test midnight, noon, 23:59:59, fractional seconds, precision truncation, and day rollover.
- **DTM-005** Client clock skew does not authorize expiry or forge created/updated times; server is authoritative.
- **DTM-006** Sort/group/filter by time agrees with displayed zone and boundary.
- **DTM-007** Relative labels (“now,” “yesterday”) update and have an absolute accessible value.
- **DTM-008** Database, API, UI, notification, calendar export, and audit preserve the same intended time.

## Comprehensive per-item coverage

- **DTM-009** Exercise absent, null, empty, zero, false, ordinary, minimum, maximum, below-minimum, above-maximum, and unknown values distinctly.
- **DTM-010** Probe powers-of-two and representation boundaries around `7/8/9`, `15/16/17`, `31/32/33`, `63/64/65`, and storage-specific limits.
- **DTM-011** Use negative, fractional, high-precision, exponential, signed-zero, NaN/infinity, overflow, underflow, and rounding cases where the type can receive them.
- **DTM-012** Use labels or serialized values containing emoticons, emoji, kaomoji, accents, RTL, combining marks, confusables, and invisible characters.
- **DTM-013** Compare UI, API, import, database, cache, queue, analytics, search index, notification, and export representations; preserve one authoritative meaning.
- **DTM-014** Send wrong types, missing fields, extra fields, duplicate keys, unknown enum members, malformed encodings, and schema-version mismatches.
- **DTM-015** Bypass client min/max/step/format constraints; enforce the server and persistence contract without clipping or coercing silently.
- **DTM-016** Switch locale, numbering system, decimal/group separator, calendar, currency, time zone, and direction; separate display formatting from stored value.
- **DTM-017** Sort, filter, group, aggregate, compare, search, paginate, and chart boundary and null values; keep ordering and totals coherent.
- **DTM-018** Create and update concurrently from two sessions; prevent lost updates, duplicate identities, and stale derived values.
- **DTM-019** Retry writes and reads across timeout, disconnect, failover, and replica lag; expose stale or uncertain state rather than false certainty.
- **DTM-020** Migrate old, missing, malformed, and newly extended values forward and backward where supported; preserve auditability and rollback.
- **DTM-021** Verify permissions at field, record, tenant, export, analytics, log, cache, and backup layers; redact consistently.
- **DTM-022** Use inert markup, SQL, template, CSV-formula, path, and log canaries in any textual representation; encode for each output context.
- **DTM-023** Check accessible names, units, errors, table headers, announcements, and non-color distinctions for input and display.
- **DTM-024** Measure validation, calculation, query, sort, aggregate, import, and export behavior at normal and supported scale.
- **DTM-025** Verify derived totals, counters, scores, dates, and statuses update atomically with source data or expose reconciliation state.
- **DTM-026** Delete, restore, archive, expire, retain, and purge values; distinguish tombstone, null, zero, redaction, and absence.
- **DTM-027** Record source, actor, old/new value, unit, time, version, and reason without leaking secrets or prohibited personal data.
- **DTM-028** Reconcile after partial failure, cache corruption, duplicate message, and delayed index update; detect and repair divergence.

[Back to Numbers, money, dates, and time index](../../numbers-money-time.md)
