Unix timestamp converter
Seconds or milliseconds ↔ ISO-8601. Live clock in this tab. Nothing is uploaded.
Now:
Ready
How it works
Unix time is milliseconds (or seconds) since 1970-01-01T00:00:00Z. JavaScript Date.now() is milliseconds. Many APIs and JWT exp claims are seconds.
Auto mode: a 10-digit integer is treated as seconds; 13 digits as milliseconds. ISO-8601 strings (with Z or an offset) parse through Date.
ULID’s first 10 Crockford characters are also a millisecond timestamp — convert here, generate IDs on the ULID page.
Examples
Date.now() → milliseconds Math.floor(Date.now()/1000) → seconds new Date(1700000000 * 1000).toISOString() // JWT exp: 1700000000 → 2023-11-14T22:13:20.000Z
FAQ
Why is my date in 1970 or year 50k? You mixed seconds and milliseconds. Switch the unit or use auto.
What timezone is “local”? Your browser’s current zone, via Date. UTC is always printed too.
Leap seconds? Unix time used here ignores leap seconds (POSIX / JS).
Does conversion leave the device? No.
Y2038? JS stores ms in a float; this page is fine past 2038. 32-bit C time_t is not.