Uniform Time Act
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The Uniform Time Act of 1966, Pub.L. 89-387, 80 Stat. 107, enacted April 13, 1966, was a United States federal law 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 (DST) is applied within the U.S. Prior to this law, each state worked out its own scheme for the dates of beginning and ending DST, and in some cases, which parts of the state should use it.
The law as originally written required states that observe DST to begin it at 02:00 local time on the last Sunday in April and to end it at 02:00 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 (effective 1987). 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 (effective 2007). However, the Department of Energy is required to report to Congress the impact of the DST extension by December 1, 2007 (nine months after the statute took effect) which the department has not done and the report is now overdue. If the DST extension failed to save energy, Congress may revert back to the old schedule set in 1986.
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:
- if the state lies entirely within a time zone, that the exemption apply statewide, or
- if the state is divided by a time zone boundary, that the exemption apply statewide or to the entire part of the state on one side of the boundary.
While there are a few areas where de facto differences within states exist, the overall pattern is simple enough, and close enough to actual practice, that it is effective and efficient
- for repeat travelers, and repeat users of long-distance telephone service, to learn the basic pattern, and
- for those in areas where de facto exceptions apply to mention the fact to those likely to be affected by it.
The most notable de facto exception is that Arizona has chosen not to use DST statewide. However, the various Native American nations within the state have the right to use DST, or not use it, as they see fit. The Navajo Nation has chosen to use DST throughout its territory, which includes parts of Arizona, New Mexico, and Utah. If it did not, then the Navajo Nation would lack a uniform time during the Summer months. On the other hand, the Hopi Nation, whose territory is surrounded by that of the Navajo Nation, and is entirely within the boundaries of the State of Arizona, has chosen not to use DST.
