Unix Timestamp Converter
Convert between Unix timestamps and human-readable dates in both directions, with automatic seconds/milliseconds detection.
How it works
- 10-digit numbers are treated as seconds, 13-digit numbers as milliseconds; ambiguous lengths fall back to a magnitude heuristic.
- Local time uses your browser's timezone; the UTC row always uses ISO 8601 with the
Zsuffix. - The date/time input is interpreted as local time in your browser, then converted to seconds and milliseconds.
About Unix Timestamp Converter
The Unix timestamp counts the number of seconds that have elapsed since 1970-01-01 00:00:00 UTC, ignoring leap seconds. It is a timezone-independent instant in time: 1700000000 is the same moment everywhere on Earth, even though it renders as different wall-clock times in different timezones. Because it is just a number, it is trivial to store, compare, and sort in logs, APIs, and databases.
The most common mistake is mixing seconds and milliseconds: JavaScript's Date.now() and many APIs return milliseconds (13 digits), while most databases and Unix tools use seconds (10 digits). Feeding a millisecond value into a seconds-based API yields a date in 1970, and vice versa. Also keep in mind that a timestamp is only a point in time — render it in the timezone your users expect — and beware the 2038 problem if anything still stores timestamps in a signed 32-bit integer, which overflows on 2038-01-19.