Milliseconds to Date

A Unix timestamp is the number of seconds (or milliseconds) elapsed since 1 January 1970 00:00:00 UTC — the Unix epoch. It is the most widely used format for storing dates in databases, APIs, and log files because it is timezone-independent and easily sortable.

Unix epoch time counts seconds elapsed since 00:00:00 UTC on 1 January 1970. This date was chosen by the original Unix designers as a convenient recent round number. It has no special significance — it predates any existing Unix system by years. All major operating systems and programming languages use this epoch as the reference point for time calculations.

Unix time was originally defined in seconds. JavaScript's Date.now() returns milliseconds (multiply by 1000) because millisecond precision is needed for browser performance measurements. Most databases, APIs, and system calls use seconds. When you see a 10-digit number it's seconds; 13-digit numbers are almost always milliseconds. This tool converts both.

A Unix timestamp is always UTC — it has no timezone. The timezone only matters when displaying a timestamp as a human-readable date. Converting 1700000000 to EST gives a different date string than converting it to JST, but the underlying number is the same. Always store and compare timestamps as UTC integers; only apply timezone offset at display time.

32-bit signed integers can represent values up to 2,147,483,647, which corresponds to 03:14:07 UTC on 19 January 2038. After that, a 32-bit timestamp overflows to a large negative number. Modern 64-bit systems are not affected. Legacy embedded systems, old 32-bit Linux builds, and some database column types (INT instead of BIGINT) are at risk.