What is a Unix timestamp?
A Unix timestamp counts elapsed time from the Unix epoch: January 1, 1970 at 00:00:00 UTC. The usual form counts seconds, while JavaScript and many APIs use milliseconds. The timestamp itself does not contain a time zone; a zone is applied only when the instant is displayed as a calendar date.
Unix timestamp examples
| Timestamp | UTC date | Meaning |
|---|---|---|
0 | January 1, 1970 00:00:00 | The Unix epoch |
1000000000 | September 9, 2001 01:46:40 | One billion seconds |
1704067200 | January 1, 2024 00:00:00 | A seconds timestamp |
1704067200000 | January 1, 2024 00:00:00 | The same instant in milliseconds |
-1 | December 31, 1969 23:59:59 | One second before the epoch |
Seconds or milliseconds?
Contemporary Unix timestamps in seconds usually contain 10 digits. Millisecond timestamps usually contain 13. Auto detection uses magnitude rather than digit count so negative and decimal values work too. Choose a unit manually whenever the source format is known.
Frequently asked questions
Does a Unix timestamp include a time zone?
No. It identifies an instant relative to UTC. The same timestamp can be displayed in New York, London or Kathmandu without changing the underlying instant.
Can timestamps represent dates before 1970?
Yes. Negative values represent instants before the Unix epoch, although individual systems may impose narrower date ranges.
Are leap seconds included?
Conventional Unix time does not represent leap seconds as distinct numbered seconds. Platform behavior around leap-second handling can vary.
Is any value sent to a server?
No. Conversion, time-zone formatting and copying happen entirely in your browser.
Technical reference: RFC 3339 date and time format. Time-zone displays use the IANA rules available in your browser; see our data sources and methodology.