Unix timestamp and UTC converter
Convert Unix seconds or milliseconds to a UTC date, or turn an explicit UTC date into a timestamp. Local calculations, no clock changes.
One instant, expressed in UTC
Change an input to update the result.
Inputs are processed in this tab. No text, paths or results are sent to our server or saved in an account. Privacy details.
From input to a useful answer.
- 01
Choose seconds or milliseconds before entering a timestamp.
- 02
Convert the value or enter complete calendar fields as UTC.
- 03
Compare the UTC result and units before copying it elsewhere.
Choose the unit before reading the date
Unix-style timestamps count time from 1970-01-01 at 00:00:00 UTC. APIs commonly exchange either seconds or milliseconds, and the unit is part of the meaning. This converter makes that choice explicit rather than guessing from the number of digits.
One second is 1,000 milliseconds. Entering 86,400 as seconds gives midnight at the beginning of 2 January 1970 UTC. As milliseconds, that same number gives only 86.4 seconds after the epoch. Check the source system’s unit even when the result looks plausible.
Calendar fields and output use UTC
Calendar fields here are interpreted as UTC, not your browser’s timezone or a remote server’s local time. The ISO output ends in Z to mark UTC. Another application can show the same instant as a different local calendar date without changing its timestamp.
Enter a complete year, month, day, hour and minute; seconds and up to three fractional-second digits are supported. Calendar validation rejects an impossible date such as 30 February. The calendar fields do not accept a local timezone name or a numeric offset.
Know the precision and range
Results are limited to UTC years 0001 through 9999. Negative timestamps represent instants before the epoch. Numeric input can contain fractions, but the calculation truncates to whole milliseconds, discarding finer precision. It is unsuitable for comparing nanosecond event timings.
Conversion follows the browser’s JavaScript Date model rather than a specialised leap-second timescale; a calendar second of 60 is rejected. For log comparisons, keep the original value and stated unit alongside the converted date. That makes display differences easier to investigate without losing the source information.
References
MDN — JavaScript Date ↗MDN — Date.toISOString and UTC output ↗A few useful answers
Why is my result in January 1970?
A common cause is selecting milliseconds for a value supplied in seconds. Check the source documentation rather than repairing the number by guessing.
Does UTC mean my computer’s local time?
No. UTC is the reference used for these fields and output. Local display needs a separate timezone conversion.
Can I retain microseconds or nanoseconds?
No. Results use whole milliseconds; any smaller fractional part is truncated.