Who follows daylight saving time and how is it regulated?
Most of the United States follows daylight saving time, but a few regions do not. Hawaii, American Samoa, Guam, Puerto Rico, the Virgin Islands and most of Arizona do not observe DST. In Arizona, the Navajo Indian territories do observe DST. Historically, local jurisdictions were allowed to decide when they would locally switch to DST, or not to observe DST at all. The Uniform Time Act of 1966 defined the rules for the dates of DST and all regions that practice DST use the same transition days. However, that same bill allows states to legislatively decide whether to practice it or not. Also, the date rules sometimes change, most recently in 1986 and 2007, extending the length of DST. The Department of Transportation (and not NIST) oversees and regulates DST.
