http://webexhibits.org/daylightsaving/c.htmlRationale & original idea The main purpose of Daylight Saving Time (called "Summer Time" many places in the world) is to make better use of daylight. We change our clocks during the summer months to move an hour of daylight from the morning to the evening. Countries have different change dates.
http://webexhibits.org/daylightsaving/e.htmlEarly adoption in lawDaylight Saving Time has been used in the United States and in many European countries since World War I.
During World War I, in an effort to conserve fuel needed to produce electric power, Germany and Austria took time by the forelock, and began saving daylight at 11 p.m. on the 30th of April, 1916, by advancing the hands of the clock one hour until the following October. This 1916 action was immediately followed by other countries in Europe, Belgium, Denmark, France, Italy, Luxembourg, Netherlands, Norway, Portugal, Sweden, and Turkey, as were Tasmania, Nova Scotia, and Manitoba. Britian began 3 weeks later, on 21 May 1916. In 1917, Australia, Newfoundland and Nova Scotia initiated it.
The plan was not formally adopted in the United States until 1918. 'An Act to preserve daylight and provide standard time for the United States' was enacted on March 19, 1918.
It both established standard time zones and set summer DST to begin on 31 March 31 1918. It placed the country on Daylight Saving Time for the remainder of WW I, and was observed for seven months in 1918 and 1919. The law, however, proved so unpopular (mostly because people rose earlier and went to bed earlier than we do today) that the law was later repealed in 1919 over President Wilson's veto. It became a local option, and was continued in a few states (Massachusetts, Rhode Island) and some cities (New York, Philadelphia, Chicago, and others).
During World War II, President Roosevelt instituted year-round Daylight Saving Time, called 'War Time.' (from 2 February 1942 to 30 September 1945). From 1945 to 1966, there was no federal law about Daylight Saving Time. So states and localities were free to choose whether to observe Daylight Saving Time and could choose when it began and ended. This, however, caused confusion -- especially for the broadcasting industry, and for railways, airlines, and bus companies. Because of the different local customs and laws, radio and TV stations and the transportation companies had to publish new schedules every time a state or town began or ended Daylight Saving Time.
On 4 January 1974, President Nixon signed into law the Daylight Saving Time Energy Act of 1973. Then, beginning on 6 January 1974, implementing the Daylight Saving Time Energy Act, clocks were set ahead for a fifteen-month period through 27 April 1975.