Unix time counts seconds since 1 January 1970 00:00:00 UTC (the “epoch”). Developers see it in JWT exp claims, database columns, and API fields because it’s timezone-neutral and easy to sort.
Seconds vs milliseconds
Classic Unix timestamps use seconds. JavaScript Date.now() returns milliseconds — a common source of off-by-1000 bugs when integrating frontends and backends.
Always mind timezones for display
Store and transmit UTC timestamps; convert to local time only in the UI. Daylight saving changes make “local midnight” arithmetic risky in server code.
Try it instantly
Convert timestamps both ways with our Timestamp / Unix Time Converter: