What is a Unix timestamp? Seconds vs milliseconds
Unix time counts from 1970-01-01 UTC. Learn how second and millisecond epochs differ and how they map to wall clocks.
A Unix timestamp is the number of seconds (or milliseconds) since 1970-01-01 00:00:00 UTC.
About 10 digits usually means seconds; about 13 digits usually means milliseconds.
Auto-detect typically uses digit length; ambiguous mid-length values need an explicit unit.
Timestamps are timezone-free instants; “Beijing time” is just formatting that instant in Asia/Shanghai.