Data

Unix Timestamp Converter

Convert an instant with explicit units, exact milliseconds, and a timezone you choose.

Choose the input meaning

Units are explicit. Seconds allow up to three fractional digits; milliseconds are integers. ISO input requires Z or a numeric offset.

The default input is the Unix epoch: zero seconds.

One instant, explicit representations

1970-01-01T00:00:00.000Z

JSON

Changing the display zone never changes the instant or assigns a meaning to an ambiguous local wall time.

Convert Unix timestamps and explicit ISO dates

Unix time counts from 1970-01-01T00:00:00Z. This converter requires you to choose seconds, milliseconds, or an ISO date with a stated offset. It reports exact epoch values, UTC ISO text, and an IANA timezone display using your browser's Intl data. It never guesses units from the number of digits.

How to use the converter

  1. Select the input format and enter its value. Seconds such as -0.001 represent one millisecond before the epoch.
  2. For ISO input, include seconds and an offset, for example 2024-11-03T01:30:00-04:00.
  3. Choose UTC or enter an IANA name such as America/New_York. Select Convert timestamp, then copy or download the JSON result.
  4. Use current instant reads your device clock once. It does not synchronize that clock with a server.

Daylight saving time and ambiguous local times

The times 2024-11-03T01:30:00-04:00 and 2024-11-03T01:30:00-05:00 are one hour apart even though their clock faces match. A date without its offset cannot distinguish those instants and is rejected. A display zone formats an already determined instant; it does not resolve a missing offset.

Precision and limits

Integer arithmetic keeps epoch milliseconds exact throughout the supported Date range of ±8,640,000,000,000,000 milliseconds. Seconds accept at most three decimal places; finer precision, exponent input, fractional milliseconds, leap seconds, 24:00, and unknown -00:00 offsets are rejected. Invalid calendar dates are not normalized into another month.

ISO input accepts four-digit years or signed six-digit expanded years, with an explicit uppercase T and Z or a numeric offset. Output UTC uses the browser's ISO Date representation. Negative epochs and year zero are supported. Timezone names and historical rules depend on the browser's installed Intl timezone database. Inputs are limited to 100 characters each; there is no remote timezone lookup.

Official references

See the JavaScript Date reference for epoch representation and range, and Intl.DateTimeFormat for timezone display behavior.

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