Unix Timestamp Converter
Convert a Unix timestamp in seconds or milliseconds to a UTC date and time, or turn a UTC date and time into Unix epoch seconds and milliseconds. You choose the unit explicitly — the tool never guesses seconds vs milliseconds — and all conversions use UTC and run locally in your browser.
How the Unix Timestamp Converter works
Unix time counts elapsed time from the epoch, 1970-01-01 00:00:00 UTC. This converter goes both ways: enter a Unix timestamp (in seconds or milliseconds) to see the UTC date and time, or enter a UTC date and time to get the Unix seconds and milliseconds. Every conversion runs locally in your browser — nothing is uploaded.
Seconds vs milliseconds
The tool does not guess the unit. You choose Seconds or Milliseconds explicitly, because the same number means very different instants depending on the unit — 1000 seconds after the epoch is 1970-01-01T00:16:40Z, while 1000 milliseconds after the epoch is 1970-01-01T00:00:01Z. Check the system or API that produced your timestamp to know which unit it uses.
Why this converter uses UTC
A Unix timestamp represents an absolute instant, not a local wall-clock time. This converter uses UTC for both directions, so your browser’s timezone and daylight saving never change the result — the same input produces the same output everywhere. It does not convert between timezones and does not model leap seconds (it follows the normal Unix/POSIX/JavaScript time model).
Can Unix timestamps be negative?
Yes. Negative values represent instants before 1970-01-01T00:00:00Z. For example, -1 second is 1969-12-31T23:59:59Z. This converter supports UTC dates from years 0001 through 9999.
Frequently asked questions
- What is a Unix timestamp?
- A count of time elapsed relative to the Unix epoch at 1970-01-01T00:00:00Z (UTC).
- Does this use seconds or milliseconds?
- Either — you select the unit explicitly. The converter never guesses.
- How do I know whether my timestamp is seconds or milliseconds?
- Check the system or API that produced it. PocketSpry intentionally does not guess from the number of digits or magnitude.
- Can Unix timestamps be negative?
- Yes. Negative values are instants before the epoch.
- What timezone does the converter use?
- UTC. Your browser timezone does not change the result.
- Can I convert a UTC date back to Unix time?
- Yes. Choose “UTC date & time → Unix timestamp”.
- Can I enter milliseconds in the UTC time field?
- No. Human date/time entry uses whole seconds. A millisecond timestamp can still be displayed with millisecond precision in the other direction.
- Does this support leap seconds?
- No. It follows the normal Unix/POSIX/JavaScript time model, which does not model leap seconds.
- Does the 2038 problem affect this converter?
- This browser converter is not limited to signed 32-bit Unix seconds, so it can convert timestamps beyond 2038 within its supported date range. Some external systems may still have their own 2038 limitations.
- Does PocketSpry upload my timestamp?
- No. This converter runs entirely in your browser.