Is my timestamp in seconds or milliseconds?

Ten digits is seconds, thirteen is milliseconds. A current timestamp in seconds starts with 17; the same moment in milliseconds is a thousand times larger. This tool detects the unit and says which it used, because reading milliseconds as seconds lands you in the year 56,000.

What is the Unix epoch?

1 January 1970 at 00:00:00 UTC. A Unix timestamp counts the seconds since then, and negative values are dates before it. The epoch is always UTC, which is why the same timestamp shows a different wall-clock time depending on the zone you read it in.

What is the year 2038 problem?

A signed 32-bit timestamp overflows on 19 January 2038. Any system still storing time in a 32-bit integer will wrap to 1901. Modern platforms use 64-bit values, but old database columns and embedded systems are still worth checking.

Unix Timestamp Converter

Convert between Unix timestamps and human dates in UTC and your local zone.

Current timestamp—

Unix timestamp

Unit

Ten digits is seconds, thirteen is milliseconds. Detection uses digit count.

Conversions

Enter a timestamp to see every representation.

Processed locally in your browser. Conversion is arithmetic done in this tab. Your local time zone is read from the browser and not reported anywhere.

Reference

What a Unix timestamp counts

A Unix timestamp is the number of seconds since 1970-01-01T00:00:00Z, ignoring leap seconds. It has no time zone: the same instant produces the same number everywhere on earth. A time zone only enters when you render that instant as a date, which is why the local time shown here differs from UTC but the timestamp does not.

Seconds or milliseconds

Unix tools, JWT claims and most APIs count seconds. JavaScript's Date.now() counts milliseconds. Mixing them is the most common timestamp bug there is, and it fails loudly in one direction and quietly in the other: a seconds value read as milliseconds lands in January 1970, while a milliseconds value read as seconds lands tens of thousands of years in the future.

Digits	Unit
10	Seconds — the classic Unix timestamp, until 2286.
13	Milliseconds — JavaScript, Java, most JSON APIs.
16	Microseconds — Postgres internals, some tracing systems.
19	Nanoseconds — Go's time.UnixNano, Prometheus.

ISO 8601

2026-09-04T12:30:45Z is the interchange format worth standardising on. The Z means UTC; an offset such as +02:00 is equally valid. A string with no zone at all is ambiguous, and different runtimes disagree about how to read it — some assume UTC, some assume local. Always write the zone.

The 2038 problem

Systems that store the timestamp in a signed 32-bit integer overflow on 2038-01-19T03:14:07Z. Anything storing it in 64 bits — which is nearly everything modern — is unaffected. It still shows up in embedded systems, old file formats and database columns typed as INT instead of BIGINT.

Questions

Is my timestamp in seconds or milliseconds?: Ten digits is seconds, thirteen is milliseconds. A current timestamp in seconds starts with 17; the same moment in milliseconds is a thousand times larger. This tool detects the unit and says which it used, because reading milliseconds as seconds lands you in the year 56,000.
What is the Unix epoch?: 1 January 1970 at 00:00:00 UTC. A Unix timestamp counts the seconds since then, and negative values are dates before it. The epoch is always UTC, which is why the same timestamp shows a different wall-clock time depending on the zone you read it in.
What is the year 2038 problem?: A signed 32-bit timestamp overflows on 19 January 2038. Any system still storing time in a 32-bit integer will wrap to 1901. Modern platforms use 64-bit values, but old database columns and embedded systems are still worth checking.