Convert Unix Time to Human Time

The number of seconds since 1970-01-01T00:00:00Z (the “epoch”), excluding leap seconds. Each Unix day is exactly 86400 seconds, even on days when an actual leap second was inserted – this is a deliberate spec choice for arithmetic simplicity.

By magnitude: values under 10¹¹ are treated as seconds (covers dates up to year 5138), 10¹¹-10¹⁴ as milliseconds, 10¹⁴-10¹⁷ as microseconds, anything larger as nanoseconds. You can override with the unit dropdown – auto-detect is a heuristic, not infallible for unusual values.

Yes. 1710443400.5 is treated as 1710443400500 ms – half a second past 1710443400. Sub-second precision is preserved in the ISO output.

The Unix timestamp 2147483647 (2038-01-19T03:14:07Z) is the maximum value for a 32-bit signed integer. Systems still using 32-bit time_t will overflow then. We flag any second-based input above this with a Y2038+ badge so you know to verify your downstream system uses 64-bit time.

The Unix value itself is always UTC-relative. The timezone selector just changes how we display the human date – using Intl.DateTimeFormat with the IANA zone you pick. Switching from UTC to America/New_York doesn’t change the underlying timestamp; it changes the wall-clock display.

“Locale full” uses your browser’s locale, set by your OS or browser language settings. Two people in different locales (en-US vs en-GB vs de-DE) see different orderings, month names, and 12/24-hour conventions for the same instant.

JavaScript’s Date object supports ±100,000,000 days from epoch (about ±273,973 years). Timestamps outside that range produce an explicit error rather than a silent Invalid Date.

Yes. -1 is 1969-12-31T23:59:59Z – one second before the epoch. Negative values are legal Unix time and represent pre-1970 dates.

Via Intl.RelativeTimeFormat using the largest non-zero unit (year/month/day/hour/minute/second) relative to your current browser clock. Month uses 30.44 days and year uses 365.25 days – common averages, not calendar-aware, so “1 month ago” can be 28-31 days off.

No. All parsing, formatting, and timezone math run in your browser via native Date and Intl APIs. The tool works fully offline once the page is loaded.