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This weekend is “fall back,” the time every year when most people in the U.S. set their clocks one hour earlier as daylight saving time ends.

It’s a rule that to many seems arbitrary and unnecessary, and research shows it can have negative impacts on our sleep cycles and overall health.

S​o why do we do it? Here's a look at the history behind daylight saving time in the U.S.

W​hen Does The Time Change?

This year, that will be at 2 a.m. on Nov. 5, which is this Sunday. It’s one of two times each year that the time changes. T​he exact days are set by federal law and have shifted over the years. The current dates went into effect in 2007 as part of the passed when George W. Bush was president.

Why Does The Time Change?

Daylight saving time was originally intended to reduce energy costs in times of war. It was first in the U.S. during World War I on March 1, 1918, according to the U.S. Department of Defense. The law was repealed after the war’s end and put in place again during the Second World War. That led to it being known as "war” time.

There were no set rules on time across the nation from the end of WWII through 1965. The of 1966 put DST into federal law and established official time zones, ending confusion over what time it was in different parts of the country.

D​oes Daylight Saving Time Really Save Energy?

It was thought that in nice summer weather – when days are already longer – people would spend more time outside and less time using electricity indoors in the evening. But whether there's any real benefit is a subject of deep debate.

A​ 2008 study by the U.S. Energy Department, after the DST "season" was extended by four weeks under President Bush, found that during the additional weeks was about .5% per day, or .03% of total electricity use for the entire year.

C​ritics say any savings are minuscule and are driven by larger economic motivations, including lobbying by retail businesses, who contend that DST leads to shopping and doing other activities in the evening.

W​hose Idea Was It?

T​here's also debate over where the idea of DST came from in the first place. Some give a nod to Benjamin Franklin, but many a New Zealand man who first proposed DST in an 1895 paper. Germany was the first country to implement it, in 1916 during World War I.

How Does Changing Time Affect Our Health?

S​cientists have linked changing time twice a year to several health and safety issues. A study in 2016, for example, found that the rate of is 8% higher in the first two days after either time change. A 2020 study connected the springtime change to a 6% rise in . And a 2017 study found the fall time change resulted in an 11% increase in symptoms of reported at hospitals.

Doctors think for these impacts is due to a lack of sunlight, as well as disruptions to circadian rhythms. Some experts think it would be better to stick with DST year-round, while others think standard time all the time would be best.

What’s Public Opinion On ‘Falling Back’ And ‘Springing Forward?’

A taken last year by YouGovAmerica showed that 59% of people in the U.S. supported year-round DST. Nineteen percent were against it, while 22% were undecided.

A move to temporarily for two years amid a nationwide gas shortage In 1974 was reversed after just a few months due to public outcry that included concern over kids going to school in the dark and an increase in traffic crashes.

Weather.com reporter Jan Childs covers breaking news and features related to weather, space, climate change, the environment and everything in between.

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