What is a Unix timestamp?
A Unix timestamp (also called epoch time) is the number of seconds that have elapsed since 00:00:00 UTC on 1 January 1970 — the Unix epoch. It is the universal language of time for computers: databases store timestamps as integers, APIs return them in JSON responses, log files use them for precise ordering, and JWT tokens use them for expiry (exp) and issued-at (iat) claims. Converting between a Unix timestamp and a human-readable date is a constant developer task, and doing it mentally is error-prone at any time zone other than UTC.
How to use this tool
- 1 In Unix → Human mode, paste a Unix timestamp (in seconds) — all formats update instantly: UTC, local time, ISO 8601, RFC 2822, relative time, and milliseconds.
- 2 Click Now to fill in the current timestamp and see today's date in all formats.
- 3 Switch to Human → Unix mode to convert a date and time back to a Unix timestamp.
- 4 Enter a date and time, choose Local or UTC timezone, and all four output formats update — Unix seconds, milliseconds, ISO 8601, and RFC 2822.
Frequently asked questions
What is the difference between Unix seconds and milliseconds?
Unix timestamps are conventionally seconds since epoch — a 10-digit integer like 1700000000. JavaScript and many modern APIs use milliseconds instead — a 13-digit integer like 1700000000000. The Milliseconds output row shows the seconds value multiplied by 1000.
What is ISO 8601 format?
ISO 8601 is the international standard for date/time strings: 2024-01-15T12:30:00.000Z. The T separates date from time, the fractional seconds are milliseconds, and the trailing Z means UTC. It is the format used by JSON.stringify(new Date()), most APIs, and database timestamps.
What is "relative time"?
Relative time shows how long ago or in the future a timestamp is from now: "5 minutes ago", "in 3 days", "2 years ago". It is recalculated at page load time based on the current moment.
What is the maximum timestamp this handles?
JavaScript's Date handles up to ±8,640,000,000,000,000 milliseconds from the epoch (roughly ±275,000 years). You will not hit a limit in practice.
Is my data sent anywhere?
No. All conversions use the native JavaScript Date API in your browser. Nothing is transmitted.