ISO 8601

Units & Measurements abbreviation · Time

ISO 8601 stands for International date and time standard (ISO 8601), a time abbreviation.

The International Organization for Standardization's standard for writing dates and times: year-month-day order, 24-hour time, week numbers, ordinal dates, time zone offsets and durations. Computing, aviation, science and data exchange rely on it to avoid ambiguity.

Example: All timestamps in the export follow ISO 8601, e.g. 2026-11-04T09:00:00+01:00.

Usage notes

First published in 1988 and revised in 2019 as a two-part standard. Besides calendar dates it defines week dates such as 2026-W45-3 (the Wednesday of week 45) and ordinal dates such as 2026-308 (the 308th day of the year). Many countries have adopted it as a national standard, and Europe published it as EN 28601.

Related abbreviations

More time abbreviations

• h – Hour
• H1 – First half
• H2 – Second half
• hh:mm:ss – Hours:minutes:seconds
• hr – Hour
• hrs – Hours (military time)
• JD – Julian date (Julian Day number)
• kya – Thousand years ago
• m – Minute (informal)
• Ma – Megaannum (million years)
• min – Minute
• MM – Month (two-digit, in date formats)

See all 51 time abbreviations →

Edited by the AbbreviationList.com team. Spotted an error or a missing meaning? Contact us.