About Unix timestamps
A Unix timestamp is a single number: the count of seconds since midnight UTC on 1 January 1970, a moment known as the epoch. It is how computers store time under the hood, because a plain number is easy to compare, sort, and do math on, with no timezones or calendars to trip over. This tool turns that number into a readable date and back, live in your browser.
Reading a timestamp both ways
Paste a timestamp and the tool shows it three ways: your local time, the same instant in UTC, and the ISO 8601 string that APIs and databases prefer. Seeing local and UTC side by side is the useful part, because a timestamp has no timezone of its own. It marks one exact instant; how it reads as a wall-clock time depends on where you are.
Going the other direction, pick a date and time and the tool gives you its timestamp in both seconds and milliseconds.
Seconds vs milliseconds
This is the trap that catches people. Classic Unix time is in seconds, and those values have ten digits today. But JavaScript and many APIs use milliseconds, which have thirteen digits. Mixing them up throws you off by a factor of a thousand, which lands you in 1970 or far in the future. This tool detects which one you pasted from the size of the number, so both just work, but it is worth knowing which your own system uses.
Timestamps are everywhere: log files, database records, JWT expiry fields, and API responses. When one shows up as a raw number, this converter tells you what moment it actually means.