Free tool · runs in your browser
Unix Timestamp Converter
Paste an epoch value or a date string to see every useful representation, including the relative time from now.
Ten digits or thirteen?
Unix time is traditionally the number of seconds since 1970-01-01T00:00:00Z, which is ten digits for current dates. JavaScript and many APIs use milliseconds, thirteen digits. Mixing the two produces dates in 1970 or in the far future.
This converter detects ten-digit values as seconds and thirteen-digit values as milliseconds. Anything else is parsed as a date string. If a value is ambiguous, append or remove three digits deliberately rather than guessing.
UTC is fixed; local time is not
The ISO 8601 output ends in Z and is always UTC. The local output depends on the timezone of the device viewing the page, including daylight-saving rules. Two people converting the same timestamp can legitimately see different local times.
When scheduling across regions, store UTC and convert at the edges. Do not store local wall-clock strings unless you also store the zone.
The 2038 problem
Systems that store Unix time in a signed 32-bit integer overflow on 2038-01-19. Modern 64-bit systems and JavaScript's millisecond numbers are not affected for practical purposes; JavaScript dates remain valid for roughly 273,000 years in either direction. The risk lives in old C libraries, embedded devices and legacy databases.
Frequently asked questions
Why is my converted time off by several hours?
Either the input was seconds treated as milliseconds (or the reverse), or you are comparing UTC with local time. Check the digit count and compare the ISO output, which is always UTC.
Does it handle dates before 1970?
Yes. Negative epoch values and dates before 1970 are supported.
Can I paste an ISO date instead of a number?
Yes. A string such as 2026-10-17T12:00:00Z is parsed as a date and converted to every output format.
What exactly is the Unix epoch?
1970-01-01T00:00:00 UTC. Unix time counts from that instant, ignoring leap seconds in most implementations.
Is the conversion affected by my system clock?
Only the relative time and the local-time rendering depend on the current clock and timezone. The epoch-to-UTC conversion itself is fixed.