Unix Epoch Timestamp Converter

A Unix timestamp — also called epoch time or POSIX time — is the number of seconds elapsed since 00:00:00 UTC on 1 January 1970. Because it is a single number with no time zone attached, it is the standard way to store time in databases, APIs, server logs, Linux systems and JWT claims like exp and iat. For example, 1700000000 is 2023-11-14 22:13:20 UTC, which is 5:13 PM the same day in New York (EST).

The most common mistake is the unit. A 10-digit value is almost always seconds; a 13-digit value is milliseconds. On Linux, date +%s prints seconds, as do PHP’s time() and Python’s int(time.time()), while JavaScript’s Date.now() and Java’s System.currentTimeMillis() return milliseconds. Treat milliseconds as seconds and you land tens of thousands of years in the future; do the reverse and you get a date in January 1970. This converter asks you to pick seconds or milliseconds explicitly, so check the digit count first.

Each conversion shows your device’s local time, UTC, the ISO 8601 string (for example 2023-11-14T22:13:20.000Z) and a relative time such as “3 days ago,” which makes it easy to line up log entries or debug token expiry. To go the other way, pick a date and time and you get both the seconds and milliseconds timestamp. The live epoch clock at the top can be paused or copied with one click.

Worth knowing: systems that store time as a signed 32-bit integer overflow after 2038-01-19 03:14:07 UTC (2147483647) — the Year 2038 problem — which is why modern platforms use 64-bit values. All conversions run locally with your browser’s Date object; nothing is sent to a server.