Date and Time Interchange Patterns
Representing instants, civil dates, time zones, recurring schedules, and intervals without hidden assumptions.
Representing instants, civil dates, time zones, recurring schedules, and intervals without hidden assumptions. Each row includes a practical application and a failure to check before using it.
Use it when
- Design time fields for an API or dataset.
- Make a schedule keep its intended local time.
Watch out for
- Examples do not describe leap-second support in every runtime.
- Time-zone databases and runtime parsing behavior must be kept current.
The data
10 rows
| Case | Example | Representation | Trap |
|---|---|---|---|
| UTC instant | 2026-10-12T09:00:00Z | RFC 3339 timestamp with an explicit UTC offset. | A local-looking timestamp without an offset is ambiguous. |
| Offset instant | 2026-10-12T12:00:00+03:00 | Timestamp identifying the same instant with a numeric offset. | An offset is not a geographic time-zone rule set. |
| Civil date | 2026-10-12 | Calendar date without a time. | Converting a birthday to UTC can change the displayed date. |
| Named time zone | Europe/Istanbul | IANA time-zone identifier for local scheduling. | Government rules can change; update the time-zone database. |
| Recurring appointment | 09:00 every Monday in Europe/Istanbul | Local rule plus named zone and recurrence. | A fixed UTC time may shift the intended local hour. |
| Unix seconds | 1791795600 | Integer count of seconds from the Unix epoch. | Do not confuse seconds with milliseconds. |
| Unix milliseconds | 1791795600000 | Integer count at millisecond scale. | Declare the unit in the field name or schema. |
| Fractional precision | 2026-10-12T09:00:00.123Z | Explicit fraction of a second. | Consumers may round or truncate to lower precision. |
| Half-open interval | start <= event_time AND event_time < end | Include the start and exclude the end. | Adjacent windows double-count a shared end if both are closed. |
| Monotonic elapsed time | performance.now() difference in a browser | Measure durations with a monotonic clock. | Wall-clock adjustments can distort elapsed-time measurements. |
Fields
The shape of this dataset, read from the data itself: every column, its type and a real value. Agents can use this to plan a query without fetching the whole document.
| Section | Field | Type | Example |
|---|---|---|---|
| data | case | string | UTC instant |
| data | example | string | 2026-10-12T09:00:00Z |
| data | representation | string | RFC 3339 timestamp with an explicit UTC offset. |
| data | trap | string | A local-looking timestamp without an offset is … |
Fetch the same bytes
The static files contain the same reference rows as the API, with no API rate limit. Live metadata, such as view counts, may differ. Use the API for content negotiation; use the static files for a cacheable snapshot.
curl "https://yjtoon.com/api/dataset/date-time-interchange?format=toon"
const res = await fetch( "https://yjtoon.com/static-data/dataset/date-time-interchange.toon" ); const toon = await res.text();
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Sources and editorial notes
Original editorial reference notes by YJTOON, informed by the linked primary documentation. External specifications retain their own licenses.
Editorial review: . Source documents keep their own licenses.