Timestamp Converter

About timestamp conversion

How does this tell a timestamp apart from a date?

A plain number (optionally with a decimal point or a leading minus sign for before 1970) is treated as a Unix timestamp. Anything else — including "now" — is parsed as a date/time string.

How does it know if a timestamp is in seconds or milliseconds?

By digit count: 10 digits or fewer is treated as seconds, more than 10 is treated as milliseconds. That threshold covers every realistic case — seconds-since-epoch stays at 10 digits until the year 2286, while millisecond timestamps for any date from the 2001–2286 range are already 13 digits.

What does the timezone selector do, and what does it not do?

It only changes which zone the converted result is displayed in — it doesn't change how typed input is interpreted. A date/time you type without an explicit UTC offset or trailing Z is parsed in your browser's local timezone, not the selected one. To specify a different source zone, include its offset directly, e.g. 2024-01-15T10:30:00+09:00.

Does this use a timezone-data library?

No — both the timezone dropdown and every converted value are powered entirely by the JavaScript engine's built-in Intl APIs, which already ship the full IANA timezone database. No dependency needed.

Does this tool upload my data anywhere?

No. All parsing and conversion happen entirely in your browser using standard Web APIs. Nothing you type ever leaves your device.