EpochLab

ISO Date Converter

Convert a date to ISO 8601, or back

The 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.

Questions people ask

The things that come up about iso date converters, answered plainly.

What is ISO 8601 format?

The international standard for writing dates and times: 2024-07-16T16:00:00Z. Largest unit first, zero-padded, with an explicit offset — the Z meaning UTC. It sorts lexicographically, which is why it is the right format to store in.

What is the T for?

It separates the date from the time. A space is permitted by RFC 3339 and accepted almost everywhere, but the T is what the standard specifies and what a strict parser requires.

What are week dates and ordinal dates?

Two other valid ISO forms for the same day: 2024-W29-2 is Tuesday of week 29, and 2024-198 is the 198th day of the year. Both turn up in manufacturing and logistics systems.

Related tools

Render an instant in any pattern or locale, and read one back out of text.

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.
Date FormatterOne date, every common output at once — ISO, RFC, SQL, filename-safe, spoken English — plus a pattern field for anything the list does not cover.
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.
ISO Week CalculatorA date to its ISO week-date form and back — `2024-W29-2` — with the ISO year, which is not always the calendar year.

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