Home/Unix timestamp converter

Epoch time, labeled clearly

Turn a timestamp into an exact instant.

Seconds and milliseconds are detected automatically. Compare UTC, browser-local time, and one named IANA zone without sending the value to a server.

Input

Timestamp or date

Values with 11 or more digits are treated as milliseconds.

The selected IANA zone determines which instant this wall time means.

Result

Representations

Seconds, milliseconds, and the same instant

Unix time counts elapsed time from 1970-01-01T00:00:00Z. Traditional Unix timestamps count seconds. JavaScript's Date constructor and many web APIs count milliseconds, which makes their current values roughly one thousand times larger.

−131 Dec 1969, 23:59:59 UTC
0Unix epoch
11 Jan 1970, 00:00:01 UTC
Negative values are before the epoch; positive values are after it.

Example: timestamp zero

0 represents the Unix epoch: 1 January 1970 at 00:00:00 UTC. In New York it was still 31 December 1969 because the local offset was behind UTC. The timestamp did not change; only its human-readable representation did.

Negative and future values

Negative timestamps represent instants before the epoch. Values beyond January 2038 also work in modern JavaScript engines, although older 32-bit systems may not store them safely. Fractional input is accepted and rounded to the date precision available in the browser.

A timestamp has no time zone. It identifies an instant. UTC offsets and regional zone rules are used only when the instant is formatted as a calendar date.

Format questions

Is ISO 8601 the same as RFC 3339?

RFC 3339 defines a practical Internet timestamp profile based on ISO 8601. The UTC output produced here, such as 2026-09-28T12:00:00.000Z, is suitable for common JSON and API use.

Why did my local time not exist?

Some regions move clocks forward for daylight saving time, skipping a block of wall-clock values. The tool rejects such a value instead of silently choosing another instant.