On February 9, 1942, “War Time”—a year-round daylight saving time—began in the United States. Passed by Congress and signed into law by President Franklin D. Roosevelt, the year-round daylight saving time required that clocks be moved ahead one hour for the remainder of the war as a national defense measure to conserve energy.
America first implemented a partial-year daylight saving time in March 1918, during World War I, and though there was popular support for the wartime measure, there was also disapproval, primarily from farmers and the railroads. The national daylight saving time was repealed after the war ended, but it continued on at the local level, especially in the North, East, and parts of the Midwest.
A national daylight saving time was again implemented during World War II, but this time, rather than lasting only part of the year, daylight saving time lasted all year. The purpose of “War Time,” as this form of daylight saving time was called, was to conserve power and provide extra daylight for war industries to increase production. As with World War I, after World War II ended, the national daylight saving time was quickly repealed, but it remained a local issue, with each state, city, and even business deciding whether it would adopt daylight saving time or not.
This patchwork form of daylight saving time caused much inconvenience and confusion, and in 1966 a national law was signed calling for daylight saving time to fall from the last Sunday in April to the last Sunday in October, with the option for states to exempt themselves. The energy crisis of the 1970s once again prompted the adoption of a year-round daylight saving time beginning in January 1974, but it actually only lasted 10 months, as legislation was signed adjusting yet again the time period of daylight saving time.
Another bill was signed in 1986 that moved daylight saving time to the period from the first Sunday in April to the last Sunday of October. This remained the law for many years until the most recent daylight saving legislation, implemented in 2007, set daylight saving time from the second Sunday in March to the first Sunday in November.
Daylight saving time has remained a contentious issue in the United States ever since it was first implemented during World War I, as people debate its effect on energy, safety, farming, and much more. However, most of the United States now follows daylight saving time, with the exception of Arizona, Hawaii, and the U.S. territories.