datoformat

Datoformat is the convention for representing calendar dates as text in computing, publishing, and data exchange. It specifies the order of day, month and year, the separators used, and whether leading zeros are included. The choice of date format is influenced by language, culture, and standards, and mismatches can cause misinterpretation and data errors.

Common formats include the ISO 8601 standard: YYYY-MM-DD, for example 2025-12-13. This format is widely used in data exchange and programming because it sorts lexicographically. Other widely used formats reflect regional conventions: MM/DD/YYYY (e.g., 12/13/2025) is common in the United States, while DD/MM/YYYY (e.g., 13/12/2025) is standard in much of Europe and elsewhere. There are also compact forms like YYYYMMDD or DDMMYYYY that omit separators.

Ambiguity is a central concern in date formatting. Two-digit years (YY) can lead to century ambiguity; using four-digit years and a standard order helps prevent errors. Some locales also use textual month representations (e.g., 13-Dec-2025) in addition to numeric formats.

In software, date formatting is handled by libraries and APIs that format or parse dates according to locale or explicit patterns. ISO 8601 is often recommended for interchange, while user interfaces typically display localized formats.

See also: date notation, ISO 8601, strftime, localization, internationalization.