ISO 8601
The international standard for writing dates and times, year first: 2025-03-04 for the fourth of March 2025.
Its two practical advantages are that it cannot be misread as day first or month first, and that it sorts in date order even when treated as plain text.
Where it comes up
- Mixed date formatsOne column holds dates written in several different styles.
- Ambiguous day and month orderA date such as 03/04/2025 could mean March 4 or April 3, and nothing in the cell says which.
See also
- StandardizationRewriting values so that everything of one kind follows one format: every date year first, every phone number in the same pattern.
- ParsingReading text and working out its structure: turning the characters 03/04/2025 into a date, or one line of a file into separate fields.