Unix Timestamp Converter

Unix (POSIX) time is the number of seconds since 1970-01-01T00:00:00 UTC, with every day counted as exactly 86,400 seconds — leap seconds are not counted, so it is not a true count of elapsed SI seconds (it trails TAI by 27 s as of 2026). Systems pass the same instant in seconds, milliseconds (JavaScript), microseconds (databases) or nanoseconds (Go, Linux). The page detects the unit from the number of digits — ten digits is seconds until the year 2286 — and says which one it used; choose it explicitly when the value is unusual (a 1970s millisecond value has fewer digits). Nanosecond remainders are kept as text; JavaScript dates carry milliseconds at most.

A timestamp is zone-free; only its rendering has a zone. UTC is computed by the ECMAScript Date; every other zone is rendered by the browser's Intl time-zone support, which carries the IANA tz database — so daylight-saving rules are whatever your browser ships, and no zone table is embedded here. Converting a date to a timestamp needs the reverse: text without an offset is read as wall-clock time in the zone you pick, resolved at that moment's offset. Inside a DST gap or overlap the result follows the zone's offset before the transition; add an explicit offset (+07:00) to remove any ambiguity.

Dates are proleptic Gregorian, as ECMAScript defines them. Leap years are divisible by 4 except centuries not divisible by 400. ISO 8601 weeks start on Monday and week 1 is the week containing the year's first Thursday, so the ISO week-year can differ from the calendar year around New Year (2021-01-03 is 2020-W53). Day of year counts from 1 in UTC. The RFC 2822 form is the one HTTP headers and email use.

Dates beyond ±100 million days from 1970 (about ±273,000 years) are outside the ECMAScript range; historical zone rules before 1970 may be approximate in any tz database; leap-second tables and TAI/GPS offsets are not applied. Everything runs on your machine; the same four anonymous usage counts as the rest of the site apply.