Prior to 2007, Daylight Saving Time (the second word is properly singular) began on the first Sunday in April; on that day, clocks were moved forward one hour in each time zone at 2:00 AM local time. Commencing in 2007, DST begins on the second Sunday in March (which in 2013 was March 10). Clocks are again shifted back in the fall; previously this return to "normal" time took place on the last Sunday in October, but since 2007 it occurs on the first Sunday in November (which in 2013 is November 3).
The purpose of the shift is to transfer, in effect, an hour's worth of daylight from the early morning hours of the day, when only milkmen and chickens are awake to appreciate it, and use it to push back sunset until one hour later in the day. This arrangement is claimed to cut electricity usage in the evening and help reduce traffic accidents.
The concept of something much like Daylight Saving Time was referenced by Benjamin Franklin in a satirical 1784 essay titled "An Economical Project." After several European countries put daylight time into practice during World War I, the United States formally adopted it in 1918, but it proved unpopular and was discontinued in 1919. (The U.S. still had a large agrarian sector back then, and far fewer businesses stayed open into the later evening hours, so most people tended to rise and retire earlier than they do today, negating the practicality of shifting an hour's worth of daylight away from early morning.)
Although some cities and states opted to continue daylight time after 1919, it did not return on a national level until World War II, when it was referred to as "War Time" and observed year-round between 1942 and 1945. From 1945 through 1966 there was no federal law in effect to establish guidelines for daylight time, leaving states and municipalities to observe it how and when they chose, if atall.
By 1966 the different daylight time practices throughout the country were a source of difficulty for businesses that had to follow strict time schedules, such as television networks and airlines, so that year Congress passed the Uniform Time Act which specified that Daylight Saving Time begin on the last Sunday of April and end on the last Sunday of October. (States were still free to pass laws exempting themselves from the daylight time scheme.) After the "energy crisis" of 1973 precipitated by an Arab oil embargo against the U.S., President Nixon signed the Emergency Daylight Saving Time Conservation Act, which put the United States on Daylight Saving Time for the fifteen-month period between January 1974 and April 1975.
In 1986 federal law was amended to start Daylight Saving Time earlier in the year, the change now occurring at 2:00 AM on the first Sunday in April and ending at 2:00 AM on the last Sunday in October. Several states and territories of the U.S. (Arizona, Hawaii, Puerto Rico, the Virgin Islands, American Samoa, Guam, and the Northern Marianas Islands) do not observe daylight time.
In August 2005, the United States Congress passed the Energy Policy Act, which changed the dates of both the start and end of daylight saving time (DST). As of 2007, DST now starts three weeks earlier (2:00 AM on the second Sunday in March) and ends one week later (2:00 AM on the first Sunday in November) than before.
Our DSTease page describes how a prankish newspaper editor put one over on the national press with his idea for a Daylight Saving Time "contest" in 1984.
Last updated: 2 November 2013
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