NATIONAL -- Daylight Saving Time adds 1 hour to standard time (at 2:00 a.m.) to make better use of daylight and conserve energy. It is observed in over 70 countries worldwide, although the beginning and end dates vary from country to country. Arizona and Hawaii are the only states that do not observe daylight saving time.

 “Fast Time,” the original name for Daylight Saving Time, was first introduced in 1918 when President Woodrow Wilson signed it into law to support the war effort during World War I. Only seven months after the conflict's end, Congress repealed the time change in 1919, although some cities, notably New York, Boston, and Chicago, continued to use it. War brought nationwide usage again when Franklin D. Roosevelt proposed year-round Daylight Saving Time in 1942.

For more than two decades -- from 1945 to 1966 -- there were no uniform rules for Daylight Saving Time. States could start and end daylight saving whenever wanted, thereby causing widespread confusion especially for train and bus schedules, and the broadcast industry. In 1966, Congress passed the Uniform Time Act, which set the last Sunday of April as the beginning and the last Sunday of October as the end of Daylight Saving Time.

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In 1986 Congress, changed the beginning of DST to the first Sunday in April, while the end remained the last Sunday in October. These start and end dates stayed in effect from 1987 to 2006, when the length of Daylight Saving was extended yet again to run from the second Sunday of March until the first Sunday of November.

* Sources:  TimeandDate.com and History.com.