8601

8601 most commonly refers to ISO 8601, the international standard for representing dates and times. It is published by the International Organization for Standardization (ISO) and defines unambiguous formats for calendar dates, times of day, time zones, durations, and intervals. The term is also used to denote the calendar year 8601 CE, or other historical references, but ISO 8601 is the common association in computing and data interchange.

Date representations in ISO 8601 include the extended form with hyphens, such as 2024-07-18, and the basic form without separators, such as 20240718. The standard also specifies week dates (YYYY-Www-D) and ordinal dates (YYYY-DDD), providing alternative ways to refer to a day within a year.

Time representations allow hours, minutes, and seconds with optional decimal fractions, for example 14:23:30 or 14:23:30.5. Times can include a time zone, using Z for UTC or an offset such as +05:00 or -04:00.

Date-time combinations are written with a T separator between date and time, for example 2024-07-18T14:23:30Z. This centralized form is widely used in data exchange and specifications.

Durations are expressed with a leading P and designators for date and time components, such as P3Y6M4DT12H30M5S. Negative durations are allowed by prefixing the entire value with a minus sign, e.g., -P3Y.

Intervals can be defined by two instants separated by a slash, such as 2024-07-18T14:00:00Z/2024-07-18T16:00:00Z, or by a start and duration, such as 2024-07-18T14:00:00Z/P1D. Recurring intervals are supported with a repetition indicator, for example R5/2024-07-18T14:00:00Z/P1D.

ISO 8601 is maintained by ISO and is widely implemented in databases, programming languages, and data interchange formats to ensure consistent date and time representation.