ISO date validator
ISO 8601 is the international standard way to write dates, like 2024-02-29 or 2024-02-29T12:30:00Z. This validator checks whether your text follows the strict form this site uses and whether the date actually exists. Developers and data teams use it to test values before saving them to a file or database.
- Runs in your browser
- Free, no account needed
- Copy or download the result
Result
Example
2024-02-29T12:30:00Z
Valid ISO instant. UTC: 2024-02-29T12:30:00.000Z
How to use the iso date validator
- Type a calendar date like 2024-02-29, or a full date and time like 2024-02-29T12:30:00Z.
- If you include a time, end it with Z for UTC or an offset such as +05:30.
- Press Run to see whether the value is valid.
- Copy result or Download to save the normalized value.
How it works
Two shapes are accepted: YYYY-MM-DD, or YYYY-MM-DDTHH:mm:ss with Z or a plus or minus HH:MM offset.
Impossible dates such as 2023-02-29 or 2024-04-31 are rejected.
A time without Z or an offset is rejected, because it does not name an exact moment.
Hours run 00 to 23 and minutes and seconds 00 to 59, so leap seconds like 23:59:60 fail. Offsets can go up to 14:00.
A valid date and time is also shown converted to UTC, with up to three fractional second digits.
Everything runs in your browser. Your input is not uploaded or stored.
Questions and answers
What is the ISO 8601 date format?
It writes the year, month and day from largest to smallest with hyphens, as YYYY-MM-DD. A time can follow after a T, as in 2024-02-29T12:30:00Z.
What does the Z at the end of a time mean?
Z means the time is in UTC, which has an offset of zero. You can use an offset like -05:00 instead.
Why is my date and time marked invalid?
Common causes are a missing Z or offset, missing seconds, a space instead of the T, or a day that does not exist in that month.
Is 2024-02-29 a real date?
Yes. 2024 is a leap year, so February has 29 days. The same day in 2023 is rejected.