What is a Unix timestamp?
A Unix timestamp (or epoch time) counts the number of seconds that have elapsed since January 1, 1970, 00:00:00 UTC, ignoring leap seconds. It's the most common way computers store and exchange points in time, because it's a single unambiguous number independent of timezone or calendar formatting.
Seconds vs. milliseconds
Unix (POSIX) time is defined in seconds, but many languages and APIs — JavaScript's Date.now() among them — use milliseconds since the epoch instead. This tool auto-detects which unit you pasted based on digit count (10 digits ≈ seconds, 13 digits ≈ milliseconds).
FAQ
Why does the timestamp field reject my input?
It must be a plain integer — no decimals, commas, or units attached.
What timezone is the date field in?
The "Date & time" field uses your browser's local timezone. The breakdown below always shows both UTC and local time explicitly so there's no ambiguity.