Unix timestamp converter: seconds and milliseconds to dates

Convert API and log timestamps to UTC and a selected time zone, or turn an offset-qualified date into Unix seconds and milliseconds.

Timestamp → date

Inputs and results are neither stored nor sent to a server.

Result

Show result

Getting started

Choose a direction. For a number from an API or log, check the original documentation for seconds versus milliseconds. The same digits mean different dates; the tool does not force a unit guess from digit count.

For date input, include a UTC offset, such as 2026-10-24T12:00:00+09:00, or Z for UTC. The display-zone selector changes how an instant is shown and does not change the offset in your input.

Compare the UTC ISO date, selected-zone date and epoch values, then copy the result you need. Check the destination program’s expected unit before pasting.

Rules and limits

Unix time starts at 1970-01-01T00:00:00Z and does not count leap seconds. Negative values precede that instant. Local clock readings can repeat or disappear at daylight-saving transitions, so date input requires an explicit UTC offset. Seconds preserve up to three decimal places; milliseconds are integers. Zone rules come from the browser. Conversion does not verify the original log’s unit or correctness.

Sources consulted

MDN — Date ↗