About Unix timestamps
A Unix timestamp is the number of seconds since 1 January 1970 at midnight UTC. It is how most software stores a moment in time, because it is a single number with no time zone or format to argue about.
Worth knowing
- Seconds are the standard; JavaScript uses milliseconds, so its numbers are a thousand times larger.
- The value is always UTC — the local time shown depends on your device.
- Negative numbers are dates before 1970.
- A signed 32-bit timestamp runs out on 19 January 2038; 64-bit storage is the fix.
Seconds or milliseconds?
A ten-digit number is seconds; thirteen digits is milliseconds. This page detects which you pasted and shows both.
Why is my timestamp off by hours?
Almost always a time zone. The timestamp is UTC; if you compare it against a local clock reading, the difference is your offset.
What is the 2038 problem?
Systems storing the timestamp in a signed 32-bit integer overflow on 19 January 2038 and wrap to 1901. Moving to 64-bit storage removes the limit for practical purposes.