A Unix timestamp (epoch time) is the number of seconds since 1 January 1970, 00:00:00 UTC. It's one timezone-independent number, which is why computers use it everywhere — operating systems, databases, logs and APIs. This converter turns a timestamp into a readable UTC date and back, showing seconds, milliseconds, ISO 8601 and how long ago the moment was.
Reviewed: June 20, 2026 · Author: Naveen P N, Founder — AI Calculator · Verified against: the Unix epoch definition, recomputed in code.
How epoch time works
Counting from a single fixed instant makes time a plain number you can store, compare and subtract — the gap between two events is just one timestamp minus the other. Leap seconds are ignored, so the count is smooth. Because it's UTC-based, the same timestamp means the same instant worldwide; your local clock only matters when you display it. Ten-digit values are seconds; thirteen-digit values are milliseconds.
Worked example — 1000000000
Scenario: decode the famous "billennium" timestamp.
The timestamp 1000000000 — celebrated by programmers in 2001 — decodes to 9 September 2001, 01:46:40 UTC. Going the other way, 27 June 2026 at 14:30 UTC is timestamp 1782570600, and the epoch for the year 2000 is 946684800. Multiply any of these by 1000 for the JavaScript-style millisecond value.
Frequently Asked Questions
Seconds since 1970-01-01 00:00:00 UTC (no leap seconds). One timezone-free number for an instant. 1000000000 = 9 Sep 2001 01:46:40 UTC.
Treat it as seconds from the epoch (×1000 for ms). 1750000000 → 15 Jun 2025 15:06:40 UTC. Use "timestamp → date" mode.
Count seconds from 1970 UTC. "Date → timestamp" mode: 27 Jun 2026 14:30 UTC → 1782570600.
Classic Unix time is seconds (10 digits). JavaScript uses milliseconds (13 digits) = seconds × 1000. Both are shown.
Signed 32-bit timestamps overflow on 19 Jan 2038, 03:14:07 UTC. 64-bit systems are fine. It's the modern Y2K.