Spring forward, fall back.

If you live in a state with daylight savings time, this may be the mnemonic device you use to remember that clocks gain an hour in March and lose an hour in November.

The idea of daylight savings time was touted by Ben Franklin, but it didn’t really catch on until World War I, reported The Economist. At that time, Britain, France and Germany decided that adding an extra hour of daylight would reduce coal usage and help the war effort, so they moved clocks forward for several months.

Changing time isn’t popular today. A survey taken in the U.S. last November found that, overall, about six in 10 Americans would prefer not to have a time change, reported Kathy Frankovic of YouGovAmerica.

Last week, the U.S. Senate unanimously passed the Sunshine Protection Act, a bill that would make daylight savings time the new permanent “standard time”. If the House of Representatives agrees the U.S. will have later sunsets all year round, beginning in 2023.

There may be economic advantages to adopting daylight savings time. Economists say that restaurants, retail stores and leisure businesses benefit from longer days, reported Angel Adegbesan of Bloomberg. There could be some disadvantages, too. Randyn Charles Bartholomew of Scientific American explained:

“Our wakefulness is governed by a circadian rhythm inside us linked to the solar cycle. Although many sleep researchers approve of ending the clock changes, they prefer the use of standard time… Less sunlight in the morning makes it harder for us humans to get started in the day, and more sunlight in the evening makes it harder to get to sleep. Darkness is a signal…that it’s time to start producing more melatonin, which is our body’s cue to lower internal temperature and start feeling sleepy. Early morning light…cause our bodies to stop melatonin production so we can feel wakeful throughout the day.”

That may be why making daylight savings time permanent was so unpopular the last time Congress did it, in the 1970s. The law was repealed after 16 months.