Unix timestamp converter

The number of seconds (or milliseconds, microseconds, nanoseconds) that have elapsed since 00:00:00 UTC on 1 January 1970, strictly excluding leap seconds. Systems store it as a plain integer, which makes it timezone-free, compact and trivially comparable — the reason logs, databases and APIs pass time around as a bare number instead of a formatted string.

History and ergonomics: JavaScript chose millisecond resolution for first-class Date math (Date.now() returns 13 digits), while Python, Go and databases kept the classic 10-digit second. Passing one where the other is expected is the most common timestamp bug — a seconds value read as milliseconds lands in January 1970. The converter above labels the detected unit so the mix-up is visible before it ships.

Almost always a local-vs-UTC mix-up: the stamp itself carries no timezone, but formatting applies one. Python datetime.fromtimestamp() renders local time while .toISOString() renders UTC — an 8-hour gap for UTC+8 users. Store UTC seconds and convert to local only for display.

At 03:14:07 UTC the signed 32-bit second counter hits 2,147,483,647 and wraps to December 1901. Modern 64-bit systems are safe; 32-bit embedded devices, binary formats and legacy columns are not. See the Y2038 countdown page for the live timer and the fix checklist.

No. Unix time pretends every day is exactly 86,400 seconds; leap seconds are silently repeated or smeared by NTP rather than mapped to separate integers. If you need true elapsed SI seconds (astronomy, GPS work), use TAI or GPS time instead.

No. Conversion runs entirely in page JavaScript — open DevTools Network and paste a value to verify zero requests. Production logs, API keys and tokens never leave your device, and the page keeps working offline after the first load.