Convert Unix timestamps, in both directions
Enter a Unix timestamp and get the date as ISO 8601, localized and as relative time, in any IANA time zone. Or pick a date and time and get the timestamp in seconds and milliseconds. Seconds versus milliseconds are detected automatically, and the current timestamp ticks live at the top. Everything runs locally in your browser, no upload.
What does a Unix timestamp actually count?
Unix time counts seconds since the Unix epoch: January 1, 1970, 00:00:00 UTC, ignoring leap seconds. One single number instead of date, time and zone: that makes instants trivially comparable and sortable, which is why operating systems, databases and APIs almost always compute with it internally. Only for display does it become a calendar date in a concrete time zone again.
Seconds or milliseconds, how does the tool know?
By magnitude. A current timestamp is about 1.75 billion in seconds but about 1.75 trillion in milliseconds, a factor of 1000 apart. The tool interprets values below 100 billion as seconds (which covers dates up to the year 5138) and larger values as milliseconds. For edge cases you can set the unit manually. Rule of thumb: 10 digits today means seconds, 13 digits means milliseconds.
What is the year 2038 problem?
Older systems store Unix time as a signed 32-bit integer. Its maximum is 2,147,483,647, reached on January 19, 2038 at 03:14:07 UTC. One second later the value wraps negative and the date jumps back to December 13, 1901. Modern 64-bit systems are safe for billions of years, but embedded devices, old file formats and 32-bit database columns remain affected. Try it: enter 2147483647.
How does the tool handle time zones and DST?
The zone list comes from your browser's IANA database (typically over 400 zones), with your local zone and UTC on top. Offsets including daylight saving time are computed by the browser's own calendar engine; the tool does not re-implement zone rules. When converting date to timestamp, the selected zone defines where the wall-clock time applies; during the ambiguous or skipped hour around a DST switch, one valid instant is chosen deterministically.
Private and offline-capable
Conversions, time-zone math and the live clock run entirely on your device via the built-in Intl API. Timestamps from logs or databases reveal when people did things, so they do not belong on anyone else's server.