What is a Unix timestamp — epoch time
What is a Unix timestamp (epoch): seconds or milliseconds since 1970-01-01 UTC and how to convert to a date online.
A Unix timestamp (epoch) is the number of seconds elapsed since January 1, 1970, 00:00:00 UTC. A single number represents a moment in time independent of timezone: local time is derived when displaying it.
A common bug is mixing seconds and milliseconds: a 10-digit number is seconds, a 13-digit one is milliseconds. Getting the units wrong can shift dates by decades, so always check the digit count when converting.
Unix timestamps are used in APIs, logs, JWT claims (iat/exp), databases, and caches. In ToolsHelper you can convert a timestamp to ISO 8601 and local time and back, and see the difference between seconds and milliseconds.
The Unix epoch is 1970-01-01T00:00:00Z. A timestamp counts seconds from that instant, not from your local midnight. Negative values are dates before 1970. Leap seconds are usually ignored, so the count is not an atomic-clock tally. This page defines the count. Turning a number you copied from a log into a date is the converter.
FAQ
Leap seconds?
Usually POSIX time without leap seconds.
How do I tell seconds from milliseconds?
About 10 digits means seconds, 13 means milliseconds. The tool detects this automatically.