What is a Unix timestamp?
A Unix timestamp (also called epoch time or POSIX time) is the number of seconds since 1 January 1970, 00:00:00 UTC, which is called the Unix epoch. It's the same everywhere in the world at the same moment, with no time zones or daylight saving to get wrong, which is why computers use it to store and compare times. Dates before 1970 are negative numbers.
Seconds, milliseconds, microseconds and nanoseconds
Unix tools and most databases count seconds (1700000000, 10 digits for today's dates).
JavaScript and Java count milliseconds (1700000000000, 13 digits), and some systems use
microseconds (16 digits) or nanoseconds (19 digits). This converter guesses the unit from the number's size;
pick one yourself if the guess is wrong.
Dates you can type
ISO 8601 dates such as 2026-10-21T14:30:00Z or 2026-10-21T16:30:00+02:00 work best.
Dates in email format, such as Wed, 21 Oct 2026 14:30:00 GMT, work too. Without a time zone, a
date and time is read as your local time, while a date alone (2026-10-21) is read as midnight UTC.
The year 2038 problem
Older systems store Unix time in a signed 32-bit number, which runs out at 2147483647: 19 January
2038, 03:14:07 UTC. One second later it wraps around to 1901. Most systems now use 64 bits, which lasts for
billions of years.