It’s time to change the clocks.

Most places in the U.S. – leaving out Hawaii and parts of Arizona – will move to daylight saving time on Sunday, March 10 at 2 a.m. That’s when we will “spring forward” and move clocks ahead one hour, shifting more daylight hours into the afternoon and evening.

DST was first implemented in the U.S. in 1918 as a way to conserve energy needed for the war effort. The idea behind “war time” was that more daylight hours would lessen the dependence on fuel. The idea waned after WWI but was brought back during World War II.

DST wasn’t the same across the U.S. until Congress passed the Uniform Time Act in 1966, which standardized DST and its start and end dates across the country. In 1973, President Richard Nixon signed into law the Emergency Daylight Saving Time Energy Conservation Act that made the time change permanent.

The current DST schedule was set by the Energy Policy Act of 2005 which went into effect in 2007 and extended daylight saving by four to five weeks. Now, DST begins on the second Sunday in March and ends on the first Sunday in November when we move to standard time and “fall back” an hour.