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Convert a Unix timestamp to a date

Paste a number and get the date, or paste a date and get the number. The awkward part of this job is that a timestamp carries no label: the same digits mean one thing in seconds and something a thousand times different in milliseconds. The unit is inferred from the length and then printed, so you can see the assumption rather than discover it later — and you can override it when the guess is wrong.

This page loads no libraries at all — the work is done by the browser itself. Your file is read on your own machine and never sent anywhere — open your browser's network tab and watch while you use it.

Questions

How does it know whether my number is seconds or milliseconds?

From how many digits it has. Twelve digits or more is read as milliseconds, fewer as seconds, and the answer says which was chosen. The reason to show it rather than decide quietly is that a wrong guess does not look wrong: read 1700000000 as milliseconds and you get a date in January 1970, which is obviously off, but the same mistake on other values lands on a believable date instead.

Can I force the unit?

Yes. Some systems emit short millisecond timestamps and some log formats keep sub-second precision separately, so the automatic rule is a default rather than a rule. Choose seconds or milliseconds and the number is read exactly that way.

Which time zone is shown?

Both. The ISO 8601 line is UTC, which is what almost every log and API uses, and the line below it is the same moment in your computer’s own time zone. Comparing the two is usually enough to explain an hour that seems to be missing.

Can it go the other way?

Yes. Paste anything the browser recognises as a date — 2024-03-14, 14 Mar 2024 10:00, or a full ISO string — and you get the timestamp in both seconds and milliseconds, along with the normalised UTC form.

Other text & code tools

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