A Unix timestamp is the number of seconds since 1 January 1970 UTC. Computers love it because it is one unambiguous number; humans hate reading it. Converting between the number and a normal date is a daily task in log files, databases and APIs.
Seconds or milliseconds?
This trips up nearly everyone. Unix time is classically in seconds (10 digits today, like 1752192000), but JavaScript and many APIs use milliseconds (13 digits). If your converted date lands in 1970 or thousands of years in the future, you have the units wrong by a factor of 1000.
How to convert
- Open the timestamp converter.
- Paste the number to get a date, or pick a date to get the number.
- Note whether the value is in seconds or milliseconds before you use it elsewhere.
The timezone gotcha
A Unix timestamp itself has no timezone — it is always UTC. The confusion comes when it is displayed: your computer may show it in local time, so the same number reads as 3pm for you and 11pm for a colleague. When comparing times across people, state UTC explicitly.
A 10-digit number is seconds; a 13-digit number is milliseconds. That quick digit count settles most conversion mistakes before they happen.