Time String Validator
Is this a valid time string?
Checks a time of day against the standard — including the edge cases that are legal and surprising, like 24:00 and the leap-second 23:59:60.
Questions people ask
The things that come up about time string validators, answered plainly.
Is 24:00 a valid time?
Yes, in ISO 8601 — it means midnight at the end of a day, and is the same instant as 00:00 the next day. Many parsers reject it, and RFC 3339 does not allow it, so it is valid and best avoided.
Is 23:59:60 valid?
Yes — it is a leap second, and both ISO 8601 and RFC 3339 permit it. It has occurred 27 times since 1972. Most software rejects it, and Unix time cannot represent it at all.
Related tools
Julian days, Excel serials, GPS time, cron expressions and format validators.
ISO 8601 ValidatorA 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.
Time ParserClock times, durations and offsets, parsed and explained — including the forms that look alike and mean different things, like `PT1H30M` and `01:30`.
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.
Time Formatter24-hour, 12-hour, with and without seconds, with an offset, as a duration — every reasonable rendering of a time of day, side by side.