Daylight saving time starts this weekend, giving most states a full eight months of extra daylight.
David Prerau, author of Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time, says each year daylight saving time lasts about 238 days.
Prerau says daylight saving time was enacted initially during World War 1.
"It was put into save energy for the wartime effort by the countries on both sides of the war, and when the U.S. got involved with World War I, we put in daylight saving time in 1918," he tells NPR's Melissa Block.
Daylight saving time was repealed after the war, but put back again in World War II for the same reasons, Prerau says.
During the 1950s and 1960s, there was no national law on daylight saving time, Prerau says, allowing towns and cities to have their own rules for when to start and end it or whether to have it at all.
"There was a bus ride you could take on Route 2 from Moundsville, W.Va., to Steubenville, Ohio. And the bus ride was only 35 miles," he says. "But because some towns along the way had daylight saving time and some didn't, if you wanted to keep your watch correct during that 35-mile ride, you'd have to change your watch seven times."