Should the U.S. Move to Permanent Daylight Saving Time?

Daylight saving time is the practice of advancing the clock one hour ahead of standard time (ST) so that people get to experience more daylight in the summer months. In the U.S., DST is observed between the second Sunday in March and the first Sunday in November. The policy seems simple, just to adjust a clock, but it's more complicated when we think about how it affects our bodies.

Humans have three different clocks that our lives and bodies must adhere to, says Dr. Elizabeth Klerman, professor of neurology at Massachusetts General Hospital and Harvard Medical School. "One is local clock time [social clock], what's on your watch, on your computer," she explains. "The second is sun time, when the sun goes up, and when the sun goes down. The third time is biological time. It's what time of day your body clock thinks it is."

Our bodies naturally follow sun time, not social time, and therefore when we switch between DST and ST, we feel groggy, tired and woefully unprepared to go to work or school after the springtime change. DST is like waking up one time zone to the east; we feel jetlagged. "Daylight saving time shifts the social clock, but not the sun clock or the body clock," Klerman says. Our bodies want to get up with the sun, not with our alarm clocks.

The U.S. Department of Transportation cites three reasons for DST:

All three claims have been studied, with mixed results. In 2008, the Department of Energy (DOE) found that the extra four weeks of DST (which were added in 2007) had saved just 0.5 percent in total electricity per day. This might not seem like much, but the DOE noted that this came out to savings of "1.3 billion kilowatt-hours — or the amount of electricity used by more than 100,000 households for an entire year."

In 2018, The New York Times reported on a 2017 study that analyzed 44 papers on the subject of DST and energy savings and found the savings even less — about 0.34 percent of electricity use. Electricity use might be less in places with milder climates but that was offset by increases in electricity use in places close the equator, the researchers said. Also, people are increasingly using energy-efficient LED lightbulbs and more energy-efficient appliances, which lower energy costs as well.

As far as traffic goes, some studies cited fewer fatal car crashes during DST because of the extra daylight during the evening rush hour. A 2007 study found an 8 to 11 percent drop in pedestrian-related crashes and 6 to 10 percent drop in car crashes in the weeks following DST. Regarding crime, one study showed that robberies reduced during DST by 7 percent and dropped a huge 27 percent during "the evening hour that gained some extra sunlight," the authors wrote.

Businesses that operate outdoors may also benefit from permanent DST. Jeremy Yamaguchi, CEO of lawncare service Lawn Love, points out that having outdoor workers start their days when temperatures are cooler is better. "After our clocks are adjusted an hour forward in the spring, what now is 8 a.m. used to be 7 a.m., meaning that workers experience the [cooler] temperatures of the early morning a little further into the day than they used to," he explains.

The tourism and travel industry could gain from permanent DST, too. Nick Mueller, director of operations for travel website HawaiianIslands.com, says that DST increases tourism revenue. "Getting that extra hour of sunlight actually boosts the amount of people who choose to travel for outdoor excursions, activities or for visiting theme parks," Mueller says. "When people go on vacation, they typically want to get the most out of their days, and DST helps with that."

Since the Senate passed the bill making DST permanent, several groups have come out against it, including the American Academy of Sleep Medicine (AASM), the National Safety Council and the National Parent Teacher Association. They said that permanent standard time is actually better for the body.

Klerman would agree. In 2019, she co-authored a paper published in Frontiers in Physiology that laid out evidence of how DST harms our health and addresses some DST fallacies. "The misconception people have is that there's more light. There's no more light; it's just shifted," Klerman explains. "If you're an evening person and there's more light at night, it will shift your body clock later. So, it's going to make life worse for later people because they still have to wake up earlier for clock time. All those later people who like it are actually getting less sleep."

The impacts aren't just happening in the week following the springtime change either, Klerman says. "It's about what's happening over the entire season," she says. "There's misalignment between the inner body clock and clock time because it's one time zone different. There's also insufficient sleep. Both of those have shown to have adverse effects on performance, cardiovascular disease, errors and accidents."

A 2014 report on cardiovascular events stated that the Monday following the shift to DST is associated with a 24 percent increase in heart attacks. The rate of suicides in men with bipolar disorders increased in the weeks following DST, according to a study spanning 30 years of Australian data.

There are also more workplace injuries (and of a more severe nature) on the Mondays following the DST shift. In the seven days following time changes, safety-related incidents increased by 4.2 percent in the spring and 8.8 percent in the fall. And a study showed the risk of fatal car crashes increases by 6 percent in the days following DST, though overall accidents during DST tend to decrease. Most of the crash increase was in the morning, which let the study authors to attribute it to sleep deprivation and circadian misalignment, along with the fact that it was darker in the morning.

The U.S. first used permanent DST for seven months during World War I. It was adopted again during World War II to conserve fuel and was officially known as "war time." When polled, only 17 percent of Americans wanted to stick with war time once the war was over, so it was stopped in 1945. The U.S. also switched to permanent DST during the energy crisis between 1974 and 1975. This time it was abandoned because some children were hit by vehicles during the dark morning hours while waiting for the school bus. (In some states, the sun didn't rise until 9 a.m. during DST.) After nine months of permanent DST, the government ended it.

Where Americans stand on the issue depends on which survey you look at. According to a 2021 Associated Press poll, only 25 percent of Americans liked to switch back and forth between DST and ST. Forty-three percent wanted permanent standard time, and just 32 percent wanted to see permanent DST. However, in a 2021 CBS News poll, the leading preference (41 percent) was to switch between DST and ST; permanent ST (28 percent) was the next-most popular option, followed by permanent DST (23 percent).

While switching to permanent DST may be less annoying than switching back and forth and boost revenue in some businesses, many experts feel it's not worth the health risks.

"Switching to permanent Standard Time would better align our bodies to daily sunrise and sunset which influences the natural sleep/wake cycles, also called circadian rhythm," said Dr. Rick Bogan, board chair of the National Sleep Foundation, in a 2021 statement. He pointed to a poll showing that 70 percent of Americans don't think their sleep, routines or moods are affected by time changes, though they are. "We're seeing gaps between what the public thinks and both published research and real-world observations of the clock change's effects on health."

Even though Yamaguchi prefers not to move to ST permanently, he knows that the benefits of DST last only a few weeks for his business and doesn't rebuke the negative impacts it can have on health. "Even though I am a business owner and am always in favor of what will benefit my employees and company the most, I do believe that public health concerns should be prioritized and considered ahead of business benefits," he says.