Unix Timestamp Converter

How it works

Unix time is whole seconds since 1970-01-01 00:00:00 UTC, ignoring leap seconds. Converting to a date uses that UTC instant; local time is then shown in this browser’s time zone. Going the other way, you choose whether the date and time you typed should be read as UTC or as local wall-clock time. Values with 13 or more digits (absolute magnitude ≥ 10^12) are treated as milliseconds — a common paste from JavaScript’s Date.now() — and the page says so rather than displaying a year-50,000 date.

Formula

UTC datetime = 1970-01-01 00:00:00 UTC + Unix seconds
Unix seconds = floor(milliseconds since epoch ÷ 1000)
If |value| ≥ 10^12: interpret as milliseconds

Worked examples

• 0 → January 1, 1970, 00:00:00 UTC
• 1700000000000 → treated as milliseconds → 1700000000 seconds → 14 Nov 2023 22:13:20 UTC

Useful notes

• Always shown with a time zone label (UTC or the browser’s local zone).
• Millisecond timestamps are detected and converted; they are not silently read as seconds.

FAQ

Is Unix time UTC?

The instant is defined from UTC. Display can be UTC or local; this tool shows both when converting from a timestamp.

Why does my 13-digit number look like the wrong century?

JavaScript often uses milliseconds. This converter treats values ≥ 10^12 as milliseconds so you do not get a date thousands of years ahead.

Does this handle leap seconds?

No. Unix time ignores leap seconds, like most programming clocks. That is a documented limitation, not a bug in this page.

Related tools

• Day of Week
• Time Duration