Unix Timestamp Converter

How to convert a Unix timestamp

1. Choose Timestamp to date or Date to timestamp.
2. For a timestamp, paste an integer and select seconds or milliseconds.
3. For a date, use a value such as 2023-11-14T22:13:20Z or 2023-11-15T03:13:20+05:00.
4. Select Convert timestamp. The result shows UTC, Unix seconds and Unix milliseconds together.
5. Copy the JSON result or download timestamp.json.

The input-unit option applies only when the input is a timestamp. Date conversion always returns both units.

What Unix time represents

Unix time measures elapsed time from 1970-01-01T00:00:00Z using the conventional epoch representation that does not count leap seconds. The same instant can be written as seconds or milliseconds. A millisecond value is one thousand times the seconds value; mixing the units can produce a date near 1970 or far into the future.

A timestamp is an instant, not a local calendar label. Output is shown in UTC using ISO notation. The tool does not use your browser timezone to guess the meaning of a date without an offset. For a local appointment or a daylight-saving transition, establish the intended timezone and offset before conversion.

Seconds, milliseconds and offsets

1700000000 seconds
1700000000000 milliseconds
2023-11-15T03:13:20+05:00

UTC: 2023-11-14T22:13:20.000Z
Unix seconds: 1700000000
Unix milliseconds: 1700000000000

These three inputs identify the same instant when the correct mode and unit are selected. Timestamp zero is the epoch itself. Negative values represent instants before the epoch; negative one millisecond is 1969-12-31T23:59:59.999Z, with Unix seconds -0.001.

Validation and precision rules

Timestamp inputs must be whole decimal integers. They are read using BigInt before range checking, so a large value is not silently rounded on input. Milliseconds must fit the JavaScript Date range of plus or minus 8,640,000,000,000,000. Output seconds can have a fractional part when the instant is not a whole second. Both exported epoch values are decimal strings so even milliseconds near the supported range boundary retain every digit.

Date input uses a documented subset: a four-digit year, calendar date, T separator, hours/minutes/seconds, optional one-to-three millisecond digits, then Z or a numeric offset. Impossible dates such as February 30 are rejected instead of rolling into March. Leap-second values, 24:00, fractional precision finer than milliseconds and an unspecified -00:00 offset are not supported.

Common timestamp mistakes

Do not infer units only from the number of digits: older dates, negative values and small test fixtures can defeat that rule. Check the originating API’s specification. A database may also use microseconds or nanoseconds, which this interface does not accept as a separate unit.

A displayed date does not tell you whether a token or record is valid. The JWT Decoder can expose NumericDate claims, but neither decoding nor converting them verifies a signature or application policy. Use JSON Viewer to find the relevant timestamp field in a response. For numeral-system changes rather than date interpretation, use the Number Base Converter.

The converter provides no current-time clock, named-zone database, date arithmetic or calendar scheduling. These are separate tasks with different ambiguity rules.

Processing and privacy

The operation runs in your browser. The tool does not send the material you enter to a processing server or automatically save it. Reset clears the form and result from the interface; it is not a secure-erasure guarantee for browser memory. Copy and download deliberately create copies outside the tool. The website itself still makes ordinary requests for its pages and scripts. See the privacy policy for the distinction.

Frequently asked questions