What a Unix timestamp is

A Unix timestamp counts the seconds since 1 January 1970 at 00:00 UTC, a moment called the epoch. It is a simple way for programs, databases and log files to store a point in time without worrying about time zones. Many systems, including JavaScript and Java, count milliseconds instead, which gives a 13-digit number today rather than a 10-digit one.

How to use it

Timestamp to date: paste a number. Values with up to 11 digits are read as seconds and bigger ones as milliseconds, and the page says which it picked. You get the UTC time in ISO 8601 form, the time in your own time zone, and how long ago or from now it is.

Date to timestamp: choose whether the date you pick is in your time zone or in UTC, pick a date and time, and copy the seconds or milliseconds. “Use now” fills in the current moment.

Questions

Why is the date one day off? Check the time zone switch. A timestamp is the same everywhere, but the calendar date it falls on depends on the zone.

What about the year 2038? Systems that store seconds in a signed 32-bit number run out on 19 January 2038. This page uses larger numbers, so it handles dates far beyond that and before 1970 (negative timestamps).

Is anything uploaded? No, the conversion runs in your browser.