8601notation

8601 notation, more formally ISO 8601, is an international standard for representing dates, times, and durations in a numeric, unambiguous format. It is designed for data exchange and computer processing, helping to avoid misinterpretation across languages and regional formats.

Date representations appear in extended form as YYYY-MM-DD or in basic form as YYYYMMDD. Time is written as hh:mm:ss with an optional decimal fraction of seconds, and a T separates the date and time. Time zones are indicated by Z for UTC or by an offset such as ±hh:mm (or ±hhmm). The standard allows combinations of date, time, and zone, as well as standalone dates or times. Additional representations include ordinal dates (YYYY-DDD) and week dates (YYYY-Www-D).

A typical date-time value is 2024-06-14T15:32:10Z, or 2024-06-14T15:32:10+02:00. In basic form, you may encounter 20240614T153210+0200. The standard also defines durations and intervals using the PnYnMnDTnHnMnS syntax, enabling expressions like a duration of five days and three hours.

Usage and variants: ISO 8601 serves as the basis for many protocols, data formats, and software libraries. RFC 3339 specifies a commonly used subset for Internet protocols. Depending on context, systems may prefer the extended form with separators for readability or the compact basic form for compactness. The notation promotes consistency in timestamps but requires careful handling of time zones to avoid ambiguity.

See also ISO 8601, RFC 3339, UTC, and time zone designators.