Does 04/05 mean April 5 or May 4? Both interpretations are ordinary in different places. The easiest way to avoid a misunderstanding is to choose a format that leaves less to guess.
For people, write the month
“April 5, 2026” and “5 April 2026” are both easy for an English-speaking reader to understand. If a date appears in an invitation, invoice, or instruction that crosses borders, a written month can prevent a costly mix-up. Include the year when the document may be saved or referred to later.
For files, use year–month–day
The ISO 8601 extended calendar-date format puts the largest unit first: YYYY-MM-DD. April 5, 2026 becomes 2026-04-05. Two-digit months and days give consistently formatted date strings a useful property: alphabetical order follows chronological order.
| Format | Same example date |
|---|---|
| Written | April 5, 2026 |
| ISO calendar date | 2026-04-05 |
| US month first | 04/05/2026 |
| Day first | 05/04/2026 |
A date is not a moment
A calendar date is useful for a birthday or an all-day task. It does not identify one instant across the world. If you are coordinating a release or a call, add a time and a zone. A timestamp ending in Z is expressed in UTC; one with a numeric offset specifies its relationship to UTC.
A useful file name: 2026-04-05-meeting-notes. Keep the date format consistent across a folder so sorting remains predictable.
Copy the right format for today
The home page gives you four date formats, based on your local time zone, with a copy button beside each one. For machine timestamps, use the Unix timestamp converter and select seconds or milliseconds explicitly.
Reference: ISO’s introduction to ISO 8601.