Unix timestamps are everywhere in software — database records, API responses, JWT expiry, log files, file metadata. Here's a complete reference for working with them across languages and environments.

What is a Unix timestamp?

A Unix timestamp is the number of seconds elapsed since the Unix epoch: January 1, 1970, 00:00:00 UTC .

0 → 1970-01-01 00:00:00 UTC 1000000000 → 2001-09-09 01:46:40 UTC 1746144000 → 2025-05-02 00:00:00 UTC

Enter fullscreen mode

Exit fullscreen mode

Timestamps store a single integer instead of separate year, month, day, hour, minute, second fields — simpler to store, sort, and compare.

To convert between Unix timestamps and human-readable dates, the Unix Timestamp Converter converts in both directions and handles millisecond timestamps too.

Seconds vs milliseconds

JavaScript (and many other environments) uses milliseconds since the epoch, not seconds:

Date .…