Unix Timestamp Converter

Unix timestamps are the lingua franca of computer timekeeping. Databases, log files, JWTs, API responses, and version-control systems all store time as a single number — seconds (or milliseconds) since the Unix epoch. Converting that number to something a human can read, and back again, is a constant task in development and debugging.

What is the Unix epoch?

The epoch is midnight UTC on 1 January 1970. A Unix timestamp counts the seconds elapsed since that instant, ignoring leap seconds. Because it is a single integer in UTC, it is unambiguous across timezones — two servers anywhere in the world agree on the same timestamp for the same moment.

Seconds vs milliseconds

This trips people up constantly. Unix systems and most databases use seconds. JavaScript's `Date.now()` and many APIs use milliseconds. A seconds value looks like `1769683200`; the millisecond version is 1000× larger. This tool auto-detects: 13 or more digits is treated as milliseconds, fewer as seconds.

Timezones and ISO 8601

A timestamp is timezone-agnostic, but a human-readable date is not. The same instant is "2:00 PM" in one city and "9:30 AM" in another. The tool shows your local time, UTC, and the ISO 8601 string (`2026-01-29T14:00:00.000Z`) — the format you should use in APIs and logs because it is sortable and unambiguous.

The Year 2038 problem

Systems that store Unix time in a signed 32-bit integer overflow on 19 January 2038, wrapping to a negative number. Modern platforms use 64-bit timestamps, which this converter supports, pushing the limit hundreds of billions of years away.