ISO 8601 Validator
Is this a valid ISO 8601 timestamp?
A strict check against the standard, with the specific rule any failure broke — and a note on whether it would also pass as RFC 3339, which is stricter still.
Questions people ask
The things that come up about iso 8601 validators, answered plainly.
Is '2024-7-16' valid ISO 8601?
No. Every field must be zero-padded to its full width, so it has to be 2024-07-16. Many parsers accept the short form anyway, which is exactly why code that works locally fails against a strict service.
Is a space instead of T valid?
Not in ISO 8601, but RFC 3339 explicitly permits it, and most parsers accept it. The validator reports both verdicts so you know which standard you are failing.
Related tools
Julian days, Excel serials, GPS time, cron expressions and format validators.
Date ValidatorChecks that a date exists as well as parses — 31 February and 29 February in a common year both parse fine in most languages, and neither is a date.
ISO Date ConverterThe extended form, the basic form, the week date and the ordinal date — all four ISO 8601 shapes for one instant, plus a parser for reading them back.
RFC3339 ConverterThe internet's profile of ISO 8601 — what JSON APIs, logs and every timestamp field in an RFC actually mean — with the differences from plain ISO spelled out.
Timestamp ValidatorChecks a numeric timestamp for the mistakes that actually happen: the wrong unit, a 32-bit overflow, a sentinel value, or a date nowhere near where it should be.