Most of us will return to standard time at 2 a.m. Sunday, Oct. 27, when clocks will be set back one hour. The change will provide an additional hour of daylight in the morning.
Under law, daylight-saving time is observed from the first Sunday in April to the last Sunday in October. Next spring, the nation will return to daylight-saving time starting Sunday, April 6.
Because daylight-saving time is a federal law, it falls to the fed to order the nation to spring forward or fall back. In the Uniform Time Act of 1966, Congress established uniform dates for daylight-saving time and transferred responsibility for the time laws to the U.S. Department of Transportation. Specifically, it's the job of U.S. Transportation Secretary Norman Y. Mineta. The plan was later seen as a fuel saving measure during the Arab Oil Embargo crisis of 1973-74. In late 1974, standard time was brought back.
Although the concept of "saving daylight" goes back to Benjamin Franklin, Daylight Saving Time was generally not adopted by countries until World War I. First, the U.S. mandatory daylight savings law was effected only during the war and President Wilson repealed it on March 31, 1918.
During World War II, daylight-savings time was reestablished by law on a year-round basis and during that time, the United States and some other countries implemented "double" daylight-saving time consisting of a two hour shift.
If it's a federal law, why then are there areas that don't observe it? The federal law does not require any area to observe daylight-saving time. But if a state chooses to observe daylight time, it must follow the starting and ending dates set by the law. In the United States, the only states that do not use daylight-saving time are Hawaii, Arizona, and most of Indiana.
Since U.S. Eastern Standard Time (EST) is UT-five hours, U.S. Eastern Daylight Time (EDT) is UT-four hours. While most of Indiana remains on Eastern Standard Time year-round (and therefore has the same time as Central Daylight Time when daylight-saving time is in effect, but is an hour different between October and April, at which point it has the same time as Eastern Standard Time), some portions near borders maintain the same time as the neighboring state, and therefore do shift to daylight-saving time. In particular, five northwest Indiana counties (Lake, Porter, La Port, Jasper, and Newton) and five southwest Indiana counties (Gibson, Posey, Vanderburgh, Warrick, and Spencer) are part of the Central Time Zone and shift to Central Daylight Time. Meanwhile, five southeast counties (Harrison, Floyd, Clark, Dearborn, and Ohio) switch to Eastern Daylight Time on their own to stay on the same time as Cincinnati and Louisville.
In Arizona, many Indian reservations do switch to daylight-saving time, while the rest of the state does not. For example, the Navajo Reservation does switch to daylight-saving time, but the Hopi reservation, located in the middle of it, does not.
No DST is observed in Puerto Rico, the Virgin Islands, American Samoa, Guam and the Northern Marianas.
Time zones: According to the U.S. Department of Transportation, time zones were first used in the United States in 1883 by the railroads to standardize their schedules. In 1918, Congress made the railroad zones official under federal law and assigned the responsibility for any changes that might be needed to the Interstate Commerce Commission, then the only federal regulatory agency.
In December 2000, Congress established the ninth U.S. time zone, the Chamorro Time Zone, for Guam and the Northern Marianas west of the International Date Line. The zone, whose time is 14 hours ahead of Eastern Standard Time, is named for the indigenous people of the region.