Convert a Unix timestamp (seconds or milliseconds since 1970) into a readable date in any timezone — or turn a date into epoch time. The current timestamp ticks live on the page.
Classic Unix time counts seconds; JavaScript uses milliseconds. 13-digit values are milliseconds, 10-digit are seconds — the tool understands both.
32-bit systems store seconds in a signed 32-bit integer that overflows on 19 Jan 2038; modern 64-bit time is fine.
Timestamps are timezone-less UTC moments; the displayed hour depends on which zone you render them in.