The United states next dabbling in time-change occurred on Feb. 9 ,1942, when Franklin Roosevelt implemented a year-round daylight saving time, calling it “war time.” This lasted until Sept. 30, 1945.
With the passing of the Uniform Time Act of 1966 daylight saving time finally become standard in the US. The Act mandated standard time across the country within established time zones. The Act also stated that clocks would advance one hour at 2 a.m. on the last Sunday in April and turn back one hour at 2 a.m. on the last Sunday in October.
Due to the 1973 oil embargo, Congress enacted a trial period of year-round daylight saving time from January 1974 to April 1975 in an attempt to conserve energy. Energy savings is often cited as the main reason for daylight saving time, however, studies have shown that any energy saved due to the use of less light is offset by an increased use of air conditioning.
Daylight saving time now starts at 2 a.m. on the second Sunday of March and ends at 2 a.m. the on first Sunday of November.
Only two states don’t observe daylight saving time, Arizona and Hawaii.