Timestamp converter

How it works

Unix time counts the seconds that have passed since 00:00:00 UTC on 1 January 1970. A ten-digit value is read as seconds; JavaScript and many systems store milliseconds instead, which is a thirteen-digit value. The auto setting treats anything below 100,000,000,000 as seconds — that number is centuries away in seconds but only 1973 in milliseconds, so the two never overlap in practice — and the selector lets you force either reading. Local time comes from the browser's own clock and time zone through Intl, and the zone in use is named in the result; the UTC row always shows the same instant regardless of where you are. The date field works in the other direction, using your local wall-clock time.

Worked example

0 is 1 January 1970 00:00:00 UTC, the instant Unix time starts. 1700000000 is 14 November 2023 22:13:20 UTC, which was a Tuesday. The same moment in milliseconds is 1700000000000 — three digits longer, which is exactly how the auto setting tells the two apart.

Questions and answers