On Sunday, November 5, at 2 a.m. local time, clocks will go back an hour, giving many (but not all) Americans an additional hour of sleep. That change will remain in effect until March of next year when clocks will go forward — and eliminate the extra hour.

Why? It goes back to the Standard Time Act of 1918 during World War I. The idea was to add more daylight hours to save energy; it also established five time zones across the U.S., USA Today reported. But the change isn’t observed everywhere in the U.S., and in many places where it is, some have called for an end to the practice. The shift may not even conserve energy as intended and can increase health risks for heart attacks and strokes, according to the Johns Hopkins Bloomberg School of Public Health.

Last year, the Senate unanimously passed the Sunshine Protection Act, which would make daylight saving time permanent, but it didn’t pass in the U.S. House of Representatives and wasn’t signed into law.