The legal and cultural expectations for date and time representation vary between countries, and it is important to be aware of the forms of all-numeric calendar dates used in a particular country to know what date is intended.

Writers have traditionally written abbreviated dates according to their local custom, creating all-numeric equivalents to day–month formats such as "28 June 2025" (28/06/25, 28/06/2025, 28-06-2025 or 28.06.2025) and month–day formats such as "June 28, 2025" (06/28/25 or 06/28/2025). This can result in dates that are impossible to understand correctly without knowing the context. For instance, depending on the order style, the abbreviated date "01/11/06" can be interpreted as "1 November 2006" for DMY, "January 11, 2006" for MDY, and "2001 November 6" for YMD.

The ISO 8601 format YYYY-MM-DD (2025-06-28) is intended to harmonize these formats and ensure accuracy in all situations. Many countries have adopted it as their sole official date format, though even in these areas writers may adopt abbreviated formats that are no longer recommended.

The Unicode CLDR (Common Locale Data Repository) Project is the world's largest repository documenting a wide variety of time and date representations for different countries and language groups.