Unix Timestamp Converter with Milliseconds

What is a Unix timestamp?

A Unix timestamp counts the seconds elapsed since January 1, 1970 at 00:00:00 UTC — the Unix epoch. It's the standard way machines store points in time: you'll find it in server logs, API responses, database columns, JWT claims like exp and iat, and cron debugging output. Compact and timezone-free, it's ideal for computers and unreadable for humans.

This converter goes both directions: paste a timestamp to get UTC, local, ISO 8601 and relative renderings, or paste a date string (or pick one from the calendar input) to get the epoch value in seconds and milliseconds. It auto-detects the unit — 10 digits or fewer is treated as seconds, more as milliseconds — which catches the single most common off-by-1000 mistake. Everything runs in your browser; nothing you enter is uploaded or logged.

When to use it

Reach for it when you're staring at raw epoch values in a log line and need to know whether that request happened before or after the deploy, when a JWT's exp claim needs sanity-checking, or when an API rejects your date and you need the exact epoch value for a query parameter or test fixture.

The dual UTC/local output matters more than it looks: a surprising number of "missing data" bugs are really a timezone offset between the server's UTC storage and the browser's local rendering. Seeing both side by side settles the question immediately, and the relative line ("3h ago") tells you at a glance whether a value is plausibly recent or wildly wrong.

Example

Paste 1700000000 and convert: you get Tue, 14 Nov 2023 22:13:20 GMT as UTC, the same instant in your local timezone, the ISO form 2023-11-14T22:13:20.000Z, and how long ago that was. Going the other way, enter 2025-01-01T00:00:00Z to get 1735689600 seconds (1735689600000 ms) — ready to drop into a query or a test. The "Copy link to this result" button encodes your input into the URL fragment so a teammate opens the page with the same conversion already done.