The American law by which we turn our clock forward in the spring and back in the fall is known as the Uniform Time Act of 1966. The law does not require that anyone observe Daylight Saving Time; all the law says is that if we are going to observe Daylight Saving Time, it must be done uniformly.
Daylight Saving Time has been around for most of this century. In 1918, in order to conserve resources for the war effort, the U.S. Congress placed the country on Daylight Saving Time for the remainder of WW I. It was observed for seven months in 1918 and 1919. The law, however, proved so unpopular that it was later repealed.
When America went to war again, Congress reinstated Daylight Saving Time on Feb. 9, 1942. Time in the United States was advanced one hour to save energy. It remained advanced one hour forward year-round until Sept. 30, 1945.
From 1945 to 1966, there was no U.S. law about Daylight Saving Time. So, states and localities were free to observe Daylight Saving Time or not.
This, however, caused confusion — especially for the broadcasting industry, and for trains and buses. 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.
By 1966, some 100 million Americans were observing Daylight Saving Time through their own local laws and customs. Congress decided to step in to end the confusion and establish one pattern across the country.
Source: United States Department of the Interior