Seconds or milliseconds — which do I have?

A 10-digit number is seconds; a 13-digit number is milliseconds. Unix time in seconds passed 1,000,000,000 in 2001 and will not reach 11 digits until 2286, so digit count is a reliable test. JavaScript uses milliseconds; most other languages and most APIs use seconds.

Why does my timestamp show a different time than expected?

Almost always a timezone. A Unix timestamp has no timezone — it is an absolute instant — so the same number renders as different wall-clock times in different places. Check whether you are reading the UTC row or the local one.

What is the 2038 problem?

Systems storing Unix time in a signed 32-bit integer overflow on 19 January 2038 and wrap to 1901. Anything using a 64-bit integer, which includes every modern language and database, is unaffected for a further 292 billion years.

Timestamp Converter

Convert a Unix timestamp to a human-readable date, or a date back to a timestamp. Handles both seconds and milliseconds, and shows the result in UTC and in your local timezone side by side. Conversion is local to your browser.

Runs in your browser — nothing is uploaded

Questions

Seconds or milliseconds — which do I have?: A 10-digit number is seconds; a 13-digit number is milliseconds. Unix time in seconds passed 1,000,000,000 in 2001 and will not reach 11 digits until 2286, so digit count is a reliable test. JavaScript uses milliseconds; most other languages and most APIs use seconds.
Why does my timestamp show a different time than expected?: Almost always a timezone. A Unix timestamp has no timezone — it is an absolute instant — so the same number renders as different wall-clock times in different places. Check whether you are reading the UTC row or the local one.
What is the 2038 problem?: Systems storing Unix time in a signed 32-bit integer overflow on 19 January 2038 and wrap to 1901. Anything using a 64-bit integer, which includes every modern language and database, is unaffected for a further 292 billion years.