IANA timezone

An IANA timezone is a canonical identifier like Europe/London, America/New_York, or Asia/Tokyofrom the IANA Time Zone Database (also called “tzdata” or “Olson database” after its original maintainer, Arthur David Olson).

Each entry captures every historical and current rule for UTC offset and daylight-saving behaviour for a region. “Europe/London” encodes: GMT (UTC+0) in winter, BST (UTC+1) in summer, the precise DST transition dates, and historical pre-1971 quirks. Pasting a date and zone into any modern programming language returns the correct offset because tzdata is built into the OS.

The naming convention is Region/City, where Region is one of Africa, America, Antarctica, Asia, Atlantic, Australia, Europe, Indian, Pacific, plus the special UTC, Etc/GMT, etc. City is a canonical city within the zone — Istanbul represents all of Turkey, New_York represents the US Eastern timezone, and so on.

Convertitive’s timezone converterworks against the browser’s OS-level tzdata via Intl.DateTimeFormat, so DST transitions and offset changes are always current without Convertitive having to ship updates.