What a Unix timestamp is
A Unix timestamp, also called epoch time or POSIX time, is the number of seconds that have passed since 00:00:00 UTC on 1 January 1970, a moment known as the Unix epoch. Because it is a single number that does not depend on time zones or calendars, it is a convenient way for programs, databases and APIs to store and compare moments in time. A timestamp of 1,767,225,600 is midnight UTC at the start of 2026.
Seconds versus milliseconds
Different systems count in different units. Classic Unix tools, PHP, Python's time module and most databases use seconds, giving a 10-digit number today. JavaScript's Date object, Java and many web APIs use milliseconds, giving a 13-digit number. This converter treats values with an absolute size of 100 billion or more as milliseconds, and smaller values as seconds, and it tells you which it chose. The date range around the present is unambiguous: seconds timestamps will not reach 100 billion until the year 5138.
Reading the results
The result shows the moment in ISO 8601 format with a Z for UTC, then your local time according to your device's time zone, and a relative description such as "3 days ago". Going the other way, choose a date and time in your local time zone and you receive the equivalent seconds and milliseconds, and the matching UTC date so that you can check the time zone conversion.
Common pitfalls
- Mixing seconds and milliseconds gives dates in 1970 or in the far future. If a date looks like January 1970, you probably have milliseconds treated as seconds in your code.
- Timestamps are always UTC. Convert to a local zone only when displaying.
- Storing 32-bit signed timestamps fails on 19 January 2038, the "Year 2038 problem". Modern systems use 64-bit values.
- Leap seconds are ignored by Unix time. Each day is treated as exactly 86,400 seconds.
Privacy
All conversions use your browser's own date handling. No data is sent to a server.