Unix timestamp converter

What a Unix timestamp is for

A timestamp identifies an instant relative to the start of 1970 in UTC. Use it to inspect logs, technical expiry times and API data when you know which unit the source system uses.

Convert a date or a number

Compare the UTC date, seconds and milliseconds. Seconds are rounded down. The Unix epoch button sets the value to zero.

1. Choose timestamp to date or date to timestamp.
2. Explicitly select seconds or milliseconds; the tool does not detect the unit.
3. Enter an integer or a full UTC date such as 2024-01-01T00:00:00Z, then convert.

The Unix epoch and units

One second equals 1000 milliseconds. When converting a date to seconds, the engine rounds down, including before the epoch: −1 millisecond becomes −1 second. Leap seconds are not represented.

Read UTC dates correctly

A trailing Z means UTC. The output does not use your device time zone and is not automatically local time. A negative value represents an instant before 1 January 1970.

Example: inspect an event time

Format and precision limits

Timestamps must be integers of up to 16 digits within the browser Date range of ±8,640,000,000,000,000 milliseconds. Dates require seconds, a trailing Z and at most three fractional digits. Offsets such as +02:00 and impossible dates are rejected. Omit thousands separators.

Sources and further reading

• ECMAScript · Time Values and Time Range