Uniform Time Act


The Uniform Time Act of 1966,, was a Law of the United States to "promote the adoption and observance of uniform time within the standard time zones" prescribed by the Standard Time Act of 1918. Its intended effect was to simplify the official pattern of where and when daylight saving time is applied within the U.S. Prior to this law, each state had its own scheme for when DST would begin and end, and in some cases, which parts of the state should use it.

History

The law, as originally written, required states that observe DST to begin it at 2 a.m. local time on the last Sunday in April, and to end it at 2 a.m. local time on the last Sunday in October and explicitly preempted all state laws related to daylight saving time per the weights and measures power given to Congress in Article 1, Section 8 of the U.S. Constitution. The law was later amended in 1986 to move the uniform start date for DST to the first Sunday in April. The latest amendment, part of the Energy Policy Act of 2005, extends DST by four or five weeks by moving the uniform start date for DST to the second Sunday in March and the end date to the first Sunday in November. The Department of Energy was required to report to Congress the impact of the DST extension by December 1, 2007. The report, released in October 2008, reported a nationwide electricity savings of 0.03% for the year of 2007.

Specifications

The law does not require that all states observe DST. Individual states may exempt themselves from DST and observe standard time year-round by passing a state law, provided:
The most noteworthy exceptions are the states of Arizona and Hawaii, the commonwealths of the Northern Mariana Islands and Puerto Rico, and the territories of American Samoa, Guam, and U.S. Virgin Islands, none of which observe Daylight Saving Time. The various Native American nations within Arizona have the right to use or not use DST. The Navajo Nation has chosen to use DST throughout its territory, which includes parts of New Mexico and Utah. In contrast, the Hopi Nation, whose territory is surrounded entirely by the Arizona portion of the Navajo Nation, has chosen not to use DST.