Seconds or milliseconds
A Unix timestamp counts from 1 January 1970 UTC. Most systems count seconds; JavaScript counts milliseconds. Ten digits is seconds, thirteen is milliseconds — this tool guesses from the length and shows both.
Your time and UTC, side by side
The timestamp itself has no timezone; it is a single instant. What differs is how you write it down. Both your browser’s local time and UTC are shown so you can see which one a log or an API actually meant.
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Frequently asked questions
Q. Why does my timestamp look ten digits long?
Because it is in seconds. Multiply by 1000 for milliseconds. A thirteen-digit number is already milliseconds.
Q. What is the 2038 problem?
A signed 32-bit timestamp overflows on 19 January 2038. Modern systems use 64-bit values, which last longer than the Sun will.
Q. Do timestamps account for leap seconds?
No. Unix time pretends every day has exactly 86,400 seconds, which is why it never has to know about leap seconds.