A number. A moment.
A readable date.

What is a Unix timestamp?

Unix time counts seconds from 00:00:00 UTC on January 1, 1970, the Unix epoch. The timestamp identifies an instant; it does not carry a city or a time zone. Changing the display zone changes the clock reading, not the number.

Seconds or milliseconds?

JavaScript’s Date.now() returns milliseconds. Many APIs and command-line tools return seconds. A modern timestamp in milliseconds normally has 13 digits; seconds normally have 10. Select the unit explicitly rather than relying on the number of digits, which is not a universal rule.

Why do local dates differ?

An instant near midnight UTC can fall on the previous or next civil date elsewhere. A timestamp remains unambiguous during daylight saving transitions, even when a local clock time repeats. To start with a local date in a city, use the world time converter, which checks for skipped and repeated times.

Precision and limitations

This tool supports dates from 1900 through 2100 and millisecond precision. Fractional seconds are accepted when they resolve to whole milliseconds. Unix time does not count leap seconds as distinct extra seconds, and this tool follows JavaScript’s date model. Negative values represent instants before the epoch.

See the JavaScript Date reference and our UTC and GMT guide.