Timestamp Converter

1. Paste a Unix timestamp in seconds, in milliseconds, or a date in ISO 8601.
2. Conversion works both ways and happens as you type.
3. Use "now" to fill in the current instant.
4. The result gives Unix in seconds and milliseconds, the local date, and relative time in plain language.

A Unix timestamp counts time since 1 January 1970 in UTC. The most common confusion is the unit: Unix systems and most APIs use seconds, while JavaScript, Java and much of the web use milliseconds.

The difference is a factor of a thousand. A millisecond timestamp read as seconds throws the date tens of thousands of years into the future, which is the classic symptom of an absurd date in your system.

Rule of thumb for present-day values: 10 digits are seconds, 13 digits are milliseconds.

The timestamp itself has no time zone: it is an absolute instant. The zone only appears when displaying it.

That is why the same input produces different times under "local" and UTC. The local time uses your computer settings, including daylight saving where applicable.

Always storing in UTC and converting only for display is the practice that avoids most date bugs in systems with users across regions.

Systems storing the timestamp in a signed 32-bit integer overflow on 19 January 2038, when the counter passes 2,147,483,647 seconds and turns negative.

Modern environments use 64 bits and have no such limit, but older databases and embedded systems still can.

This tool works across the full JavaScript date range and rejects values outside it, rather than silently returning an invalid date.