๐ ISO 8601 Validator/Parser
Supports YYYY-MM-DD, or YYYY-MM-DDTHH:mm:ss[.fff][Z|ยฑHH:MM|ยฑHHMM|ยฑHH].
โ Valid ISO 8601
| Year | 2025 |
| Month | 01 |
| Day | 01 |
| Hour | 00 |
| Minute | 00 |
| Second | 00 |
| Timezone | Z |
Enter a date or date-time string to validate whether it conforms to the international standard ISO 8601 format, and if valid, break it down into its year, month, day, time, and timezone components. Handy for checking the timestamp format used by an API response or log.
How to use
- Enter the date/time string you want to validate.
- Whether it's valid ISO 8601 and its components are shown automatically.
How the calculation works
This tool checks whether a string is a valid ISO 8601 date or date-time and splits it into year, month, day, hour, minute, second and time zone. It starts with the current time in UTC. What it checks โข Format: sequences such as 2026-09-19 or 2026-09-19T21:00:00+09:00 โข Date: month 1โ12 and a day that exists in that month (including February 29 in leap years) โข Time: hour 0โ23, minute 0โ59, second 0โ59 (a leap second of 60 and 24:00:00 for the end of the day are also accepted) โข Time zone: Z (UTC) or an offset such as +09:00, +0900 or +09 A space is accepted as well as T between the date and time, as RFC 3339 allows.
Worked example
2026-09-19T21:00:00+09:00 โ valid (21:00 in Japan) 2026-09-19T12:00:00Z โ valid (12:00 UTC, the same moment) 2024-02-29 โ valid (leap year) 2026-02-29 โ invalid (2026 is not a leap year) 2026-09-19T12:99 โ invalid (minutes go up to 59) 2026/09/19 โ invalid (slashes are not ISO 8601)
Things to be aware of
- Week dates (2026-W38-6), ordinal dates (2026-262) and durations (P1D) are not covered by this tool.
- A date-time without a time zone does not say where it applies. When exchanging data between systems, adding Z or an offset like +09:00 is safest.
- Fractional seconds up to 9 digits (nanoseconds) are supported.
FAQ
What is ISO 8601?
Itโs an international standard for representing dates and times, with common forms like โYYYY-MM-DDโ (e.g. 2025-01-01) and โYYYY-MM-DDTHH:mm:ssZโ for date-time with a timezone.
How are nonexistent dates (like February 30) handled?
Even if the format looks correct, a calendar date that doesnโt exist (e.g. February 30, 2025) or an out-of-range time such as 25:00 or minute 99 is judged invalid. February 29 is only judged valid in an actual leap year.
What range of ISO 8601 formats are supported?
Date-only (YYYY-MM-DD) and date-time formats including hours, minutes, seconds, fractional seconds, and time zone (Z, ยฑHH:MM, ยฑHHMM or ยฑHH) are supported. Week-date format (YYYY-Www) and duration format are not covered.