Unix timestamp converter
Make an event timestamp readable or create an epoch value from an explicit UTC date and time. The unit is always a choice you make, not a guess.
Unix timestamp converter
Runs on your deviceSeconds and milliseconds are different units
A Unix timestamp describes a time relative to the epoch at 1970-01-01T00:00:00Z. Many systems count seconds; JavaScript date values usually use milliseconds. One second is 1,000 milliseconds. A value interpreted in the wrong unit can point to a completely different date. Choose the unit based on your source’s documentation instead of guessing from a number’s length.
UTC removes an avoidable ambiguity
The date field in this tool is explicitly UTC. It is not interpreted in your local device timezone, even if the date picker uses a familiar local display format. Output uses an ISO string ending in Z to mark UTC. If another system displays the same instant in a local timezone, the clock reading and sometimes the calendar date can differ without the underlying moment changing.
Precision and range are explicit
Timestamp inputs must be safe whole numbers. Seconds output floors to a complete second, including for negative timestamps, while milliseconds retain the millisecond value. The converter uses the browser’s date range and Unix-style time convention; it is not a tool for modeling leap-second tables or a specialized historical time scale. A formatted timestamp does not prove when an event actually occurred or whether a device clock was correct.
Worked examples
| Input | Unit | UTC output |
|---|---|---|
| 0 | Seconds | 1970-01-01T00:00:00.000Z |
| 1 | Seconds | 1970-01-01T00:00:01.000Z |
Good questions.
Does the date field use my local timezone?
No. Its label says UTC and the tool treats the entered clock reading as UTC.
Why did the date look wrong by decades?
Check whether a milliseconds value was interpreted as seconds or the reverse.
Are negative values allowed?
Yes. Valid negative timestamps represent times before the epoch.
References & further reading
Updated 5 November 2026 · Methods & corrections