Turn a Unix epoch timestamp into a readable UTC and local date, or convert a date back into epoch seconds and milliseconds. Everything is calculated locally in your browser.
The timestamp is read as an integer; if it has 13 digits or more it is treated as milliseconds, otherwise as seconds.
No. Everything runs in your browser, nothing is uploaded, no server processes your input.
A date with no timezone (for example 2026-10-12 16:30:00) is read as UTC, so the epoch is the same for every visitor and round-trips with the epoch-to-date direction. A value that carries Z or an offset such as +08:00 uses that offset instead. The assumption used is shown in the output.