About this site

whattimezoneiam.com answers one question quickly: which time zone your device is on right now, with its UTC offset, abbreviation and next clock change. The state guides cover the places where that answer is often confusing, such as states split between two zones and Arizona's year-round standard time.

Where the times come from

Every clock and offset on the site is calculated in your browser, using your device's clock and the time zone rules that ship with the browser. Those rules come from the IANA time zone database, the same data used by phones, computers and servers worldwide. When a country changes its rules, browsers pick up the change in their regular updates.

The optional location check uses tz-lookup, a compact map of time zone boundaries built from timezone-boundary-builder. It runs inside the page.

How the guides are checked

Time zone boundaries in the US are set in federal regulations, 49 CFR Part 71, and daylight saving time follows 15 U.S.C. § 260a. Facts in the state guides are checked against those and the sources listed at the bottom of each guide, and each guide shows the date it was last checked.