Unix Timestamp Converter

Unix time, also called POSIX time or epoch time, is a single integer: the count of seconds elapsed since 00:00:00 UTC on 1 January 1970, the moment the standard calls the epoch. That anchor was chosen in the early 1970s by the team building Unix at Bell Labs, and it stuck. Because the value is one number tied to UTC rather than to any local clock, a moment recorded in Tokyo and a moment recorded in London compare directly: the larger integer is the later event, with no timezone math in between. A timestamp like 1714694400 is 8 characters of ASCII, sorts as plain text or as a number, and means the same thing on every operating system, database, and programming language that reads it. That portability is why logs, file modification times, JSON web tokens, database rows, and HTTP caching headers all lean on it. The number grows by exactly 86400 each day, 3600 each hour, and 60 each minute, so 1714694400 and 1714694460 sit precisely 1 minute apart no matter where either was recorded.

The 1 subtlety that trips people up is that Unix time is not a literal count of every physical second since 1970. It deliberately ignores leap seconds, the 27 extra seconds the world's clocks have inserted since 1972 to keep UTC aligned with the Earth's slightly irregular rotation. A Unix day is always exactly 86400 seconds, so on a leap-second day the counter either repeats or skips a value to stay on that fixed 86400 grid. This keeps the arithmetic simple, converting a timestamp to a date is just division and modulo, at the cost of being a few dozen seconds off from true elapsed physical time. For almost every application that trade is invisible and correct; only systems doing sub-second astronomical or metrological work ever need to care.

Everything here runs in your browser using the JavaScript Dateobject, so no timestamp, log line, or date you paste is sent anywhere or stored. Enter an epoch value in either seconds or milliseconds and it renders 4 views at once: your local time in full, the UTC form, the ISO 8601 string that APIs and databases prefer, and a plain-English relative time such as 3 hours ago that updates live against a 1-second clock. Go the other way by picking a date and time to read back both the seconds and milliseconds forms. The date-to-epoch field interprets the wall-clock time you type in your own browser timezone, which is usually what you want, but it means the same input produces different epoch values for users in different zones, so when a moment must be unambiguous, enter or read it as UTC. The tool does not model timezone rules, daylight-saving transitions, or historical calendar quirks beyond what the browser's own Date implementation provides, and it does not adjust for leap seconds, because Unix time itself does not. Treat the output as an exact conversion of the number you gave it, not as a statement about which zone or unit your source system actually meant.