Unix Timestamp Converter

Convert seconds or milliseconds between Unix timestamps and dates.

Reviewed: 2026-07-21

Method and assumptions

Interpret a value as seconds or milliseconds elapsed since 1970-01-01 00:00:00 UTC, showing both a UTC ISO date and the device's local representation. In the other direction, the entered local date is interpreted with the current device time zone and returned in both units. Conversion stays in the browser and is not synchronized with server or network time.

How to use it

Enter a timestamp and select seconds or milliseconds.
Compare the UTC ISO output with the browser-local date and time.
For reverse conversion, enter a local date-time and copy either unit.

When it helps

Reading numeric times from application logs
Converting an expiry time for an API request
Checking whether a value uses seconds or milliseconds

How to verify the result

Check input units and reference dates first. For an important decision, compare the result with an official source or original document. A rounded display can differ slightly from the underlying value.

Frequently asked questions

What is the difference between 10-digit and 13-digit timestamps?

Near the present era, 10 digits commonly indicate seconds and 13 digits commonly indicate milliseconds. Confirm the unit in the data specification instead of relying only on length.

Does a Unix timestamp contain a time zone?

No. It represents elapsed time from the UTC epoch. A time zone is applied only when displaying that instant as a human-readable local date.

Can the converted result differ across devices?

The UTC ISO result is consistent for the same value, while the local display can differ according to the device time zone and its supporting data.

Unix Timestamp Converter