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Daylight Saving Time

when clocks are set ahead of "standard time" by one hour

In the United States, Canada, and some other nations, Daylight Saving Time runs from the second Sunday in March through to the first Sunday in November, with the start and stop times officially being 2 A.M.

The idea of using Daylight Saving Time (DST) to take advantage of longer days during the Spring and Summer was first proposed by Benjamin Franklin in 1784, but nationwide observance of DST did not become feasible until adoption of time zones in 1883. Soon after outbreak of World War I, the practice was adopted by many European nations that had previously rejected its observance. During World War II, the United States was on Daylight Saving Time almost continuously from February 3, 1942 to September 30, 1945; it was known as "War Time."

The Uniform Time Act went into effect in the United States in 1967. It proclaimed that all states, the District of Columbia, and U.S. possessions were to observe Daylight Saving Time starting at 2 A.M. on the last Sunday in April and ending at 2 A.M. on the last Sunday in October. Any state could exempt itself by law, and a 1972 amendment to the act authorized the states split by time zones to consider that split in exempting themselves. Arizona, Hawaii, part of Indiana, Puerto Rico, the Virgin Islands, and American Samoa are now exempt. The Department of Transportation, which oversees the act, has modified some local boundaries in Alaska, Florida, Kansas, Michigan, and Texas over the last several years to reflect local differences in observance of Daylight Saving Time.

Daylight Saving Time was extended by Congress during 1974 and 1975 to conserve energy, but the country then returned to the previous end-of-April to end-of-October system until 1987, when new legislation went into effect. The new bill, signed by President Ronald Reagan on July 8, 1986, moved the start of Daylight Saving Time up to the first Sunday in April, but it did not change the end from the last Sunday in October. A 2007 bill, signed by President Bill Clinton, changed the start of DST to the second Sunday in March and the end to the first Sunday in November. Most of the world's industrialized nations have since adopted the standard used by the United States and Canada.

Benjamin Franklin
Time Zones
World War I
World War II
Department of Transportation
President Ronald Reagan

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This page was last updated on 03/10/2017.