How to use this tool
Select the conversion direction and timestamp unit explicitly. Unix time counts seconds since January 1, 1970 at 00:00:00 UTC, excluding leap seconds. ISO input must include an offset, such as Z or +05:00, so the instant is unambiguous. Millisecond conversion retains three fractional digits. Dates are limited to years 1–9999.
Try these values
Timestamp 0 seconds is 1970-01-01T00:00:00.000Z. Timestamp 1000 milliseconds is one second after that. The ISO date 1970-01-01T05:00:00+05:00 also represents timestamp 0.
Check the unit before debugging the date
A timestamp in milliseconds is one thousand times a timestamp in seconds. Mixing them up can produce a date decades away from the one you expected. Select the unit explicitly instead of relying on the number of digits, especially for old, negative or test timestamps. The UTC result gives you a common reference before you compare the time with a local log or database field.
Keep the offset in ISO input
An input ending in Z is UTC. An input ending in +05:00 describes a clock five hours ahead of UTC, and the converter accounts for that offset. Without one, the same written time could refer to many instants, so it is rejected. Milliseconds are retained when that output unit is selected; seconds output represents the containing Unix second rather than a rounded fractional second.
Common questions
How do seconds and milliseconds differ?
There are 1,000 milliseconds in a second. Choose the input unit rather than guessing from digit count.
Can I convert negative timestamps?
Yes. Negative values represent instants before the Unix epoch.
Are leap seconds counted?
Unix timestamps do not count leap seconds as additional seconds.
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