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EPOCH <-> DATE · Local tool

Epoch Converter

Convert a Unix timestamp to a date and back, in any of the four units.

Last updated

How do I convert a Unix timestamp to a date?

Paste the number into filetity's epoch converter and it works out the unit from how many digits it has, because that is the only signal a bare timestamp carries: ten digits is seconds, thirteen milliseconds, sixteen microseconds, nineteen nanoseconds. You get ISO 8601, the RFC 1123 form, the same instant in your own timezone, the day of the week, and the value in all four units, each with a copy button. It goes the other way too, and a date written with no timezone is read as UTC rather than as your own, because JavaScript reads a bare date as UTC and a bare date with a time as local, which is exactly how people end up hours out. The clock is only read when you ask, so the page does not tick while you are reading it.

  1. 01 / Your device

    the file stays here

  2. 02 / Browser memory

    the work runs locally

  3. 03 / Back to you

    saved on this device

When you would use this

Situations, not settings.

A timestamp in a log or a database row
Paste it and the unit is worked out from its length, so you do not have to remember whether that system writes seconds or milliseconds.
A date that has to go into an API as a number
Type the date and take whichever unit the API wants. A date with no timezone is read as UTC, so two people in different places get the same number.
A date that came out wrong by a factor of a thousand
The classic seconds against milliseconds mistake. Switch the unit and the year stops being 1970 or 56000.

How it works / no cloud

A conversion engine, not an upload form.

The unit is worked out from how many digits the number has, because that is the only signal a bare timestamp carries: ten digits is seconds, thirteen milliseconds, sixteen microseconds, nineteen nanoseconds. The clock is read only when you press the button, so the page does not tick while you are reading it.

  • Offline ready
  • Installable app
  • No file limit queue

Straight answers

No accordion. Nothing hidden.

Is it free?
Yes, with no watermark and no page limit.
Does it need an account?
No. There is no account system.
Is my file processed on my device?
Yes. The file is read by your browser and never uploaded. There is no server to send it to.
What formats are supported?
A timestamp in seconds, milliseconds, microseconds or nanoseconds. Out as ISO 8601, RFC 1123, your own timezone and the day of the week.
What are the limits?
Dates outside the range a JavaScript date can hold, about 273,000 years either side of 1970, are reported rather than guessed at. That almost always means the unit is wrong.
Does it work on mobile?
Yes, on any modern mobile browser. Large files are limited by the memory the phone gives the browser.
Does it work offline?
Yes, once the page has loaded. The tool keeps working with no network connection.
How do I know if my timestamp is seconds or milliseconds?
Count the digits. Around now a timestamp in seconds has ten and one in milliseconds has thirteen, with microseconds at sixteen and nanoseconds at nineteen. That is the only signal a bare number carries, and it is what this page uses, though you can override it.
Why does my date come out in 1970 or in the year 56000?
The unit is wrong. Reading milliseconds as seconds multiplies the date by a thousand and lands you tens of thousands of years out; reading seconds as milliseconds divides it and puts you a few days after 1970. Switch the unit and the date will look sensible immediately.
Is a date with no timezone read as mine or as UTC?
As UTC, deliberately. JavaScript reads a bare date as UTC and a bare date with a time as local, which means two nearly identical strings behave differently, and that is how people end up hours out. Both are read as UTC here. Add an offset such as +05:30 to be explicit.
Why does the page not show a live clock?
Because a relative line that updates while you are reading it moves under you, and because reading the clock during a render is impure. The current time is read when you press the button, and the result is anchored to that moment.
What is the epoch, and why 1970?
Unix time counts seconds from midnight UTC on 1 January 1970, which is simply when the convention was set at Bell Labs. There is nothing significant about the date; it was recent when it was chosen, and everything since has inherited it.

Keep working locally

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