How to use it
- Timestamp to date. Paste the number. The converter says whether it read seconds or milliseconds and shows the moment as ISO 8601 in UTC, as a full UTC date, in your local time and as ISO 8601 with your UTC offset.
- Date to timestamp. Pick a date and time and say whether they are in UTC or in your time zone. You get the timestamp in seconds and milliseconds.
- The current timestamp at the top updates every second. Copy it, or press Convert this to put it in the field.
How it works
A Unix timestamp counts seconds from 1 January 1970, 00:00:00 UTC, ignoring leap seconds, as Unix systems do. Converting is multiplication: seconds × 1,000 give the milliseconds that JavaScript and many APIs use, and the browser turns those into a calendar date.
- Values with 12 digits or more are read as milliseconds; shorter ones as seconds. A fraction of a second, such as
1700000000.5, is allowed. - Converting a date back gives whole seconds rounded down, as
date +%sdoes. - Local time and your offset are shown only in your browser, because only your device knows your time zone.
Worked example
1700000000:
- 1,700,000,000 seconds is 19,675 days and 80,000 seconds;
- 19,675 days after 1 January 1970 is 14 November 2023, and 80,000 seconds is 22 hours, 13 minutes and 20 seconds;
- so the moment is 2023-11-14T22:13:20Z, which is 5:13:20 pm the same day in New York (UTC−5).
The other way: 1 January 2026, 00:00 UTC is 20,454 days after the epoch (56 years with 14 leap days), × 86,400 = 1767225600.
Common mistakes
- Seconds where milliseconds are expected, or the other way round: the date lands in January 1970 or tens of thousands of years ahead. Check the number of digits.
- Reading UTC as local time. ISO 8601 strings ending in
Zare UTC; compare them with your local time row. - To convert a clock time between cities rather than a timestamp, use the time zone converter.