ISO 8601 Date Formatter
Convert any date, time or Unix timestamp into every ISO 8601 format: UTC, offset, week and ordinal.
Type a date above — every ISO 8601 form updates as you type. ISO strings, Unix
timestamps, now and everyday dates like 15 March 2024 14:30
are all understood.
- Date & time (offset) RFC 3339 / ISO 8601 extended
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- UTC (Zulu) The usual API format
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- UTC with milliseconds Millisecond precision
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- Basic (compact) No separators — filenames, IDs
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- Calendar date YYYY-MM-DD
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- Time of day hh:mm:ss
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- Week date YYYY-Www-D
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- Ordinal date YYYY-DDD (day of year)
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- Year & month YYYY-MM
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- UTC offset ±hh:mm
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- Unix seconds For comparison
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How it works
ISO 8601 is the international standard for writing dates and times so that they sort
correctly and mean the same thing everywhere: largest unit first, zero-padded, with an
explicit UTC offset — for example 2024-03-15T14:30:00Z. Paste any date into
the box and this formatter parses it, then shows every ISO 8601 representation at once:
the extended date-time with offset (also known as RFC 3339, the shape JSON APIs expect),
the UTC "Zulu" form, a millisecond-precision variant, the basic compact form without
separators, plus the calendar date, time of day, week date, ordinal date and the raw UTC
offset.
Input is flexible: ISO strings, Unix timestamps in seconds or milliseconds, the word
now, and human dates such as March 15, 2024 2:30 PM. A date
written without a time zone is read in your local time zone, so pick a zone from the
dropdown to see how the same instant is written elsewhere — daylight saving time is
applied for the date you entered, not for today. Everything runs in your browser using
the built-in Date and Intl APIs: no request leaves the page,
nothing is logged, and it keeps working offline.
Frequently asked questions
What is the ISO 8601 date format?
ISO 8601 writes dates and times largest unit first and zero-padded, so they sort alphabetically and mean the same thing in every country: 2024-03-15T14:30:00Z. The T separates the date from the time and the trailing Z means UTC; an offset such as +01:00 can be used instead. The standard also defines a week date (2024-W11-5), an ordinal date (2024-075) and a basic form without separators (20240315T143000Z), and this formatter shows all of them at once.
How do I convert a date to ISO 8601?
Paste the date into the box at the top. ISO strings, Unix timestamps in seconds or milliseconds, the word "now" and everyday dates like "15 March 2024 14:30" are all understood, and the ISO 8601 forms appear instantly. Pick a time zone from the dropdown to see how the same instant is written elsewhere, then use the Copy button next to the format you need.
Is my data uploaded anywhere?
No. The whole conversion runs in your browser with JavaScript's built-in Date and Intl APIs. Nothing you type is sent to a server, nothing is stored, there are no ads or trackers, and the page keeps working with no internet connection.