Daylight Saving Time: Pros, Cons and Tips from UVA Experts

Sitting across a desk from one another on the fourth floor of the Physical Life Sciences Budling, University of Virginia biology professors Ali Güler and Iggy Provencio admitted their differences.

“Between the two of us,” Güler said, “we’re probably living like four or five hours apart. I wake up as early as 4 a.m. What time do you wake up?”

“Without an alarm,” Provencio responded, “maybe 10.”

“So, six hours apart,” Güler said. “It’s like we’re not even living in the same country.”

The early bird and the night owl had just spent a half-hour of their morning discussing daylight saving time versus standard time, whether the biannual clock-changing in the United States is still worth it and what the best possible alternatives are going forward.

Like Güler and Provencio, different people abide by different patterns. Some have their most energy in the morning, but are in bed before 9 p.m. Others might feel their most productive in the evening, but might need an extra cup of coffee to get going in the morning.

UVA biology professors Ali Güler (left) and Iggy Provencio agree that perennial standard time offers the most health benefits. (Contributed photos)

The former, then, might favor standard time, when the sun rise typically aligns with a wake-up call, while the latter might prefer daylight saving time and its later sunsets.

In this case, though, the latter, Provencio, has a Ph.D. from UVA in biology and teaches a course called “Biological Clocks.”

“Intellectually, I prefer standard time,” he said. “Emotionally, I prefer daylight saving time because I’m pretty much an owl and I would prefer to have more light in the evening. But intellectually, I can’t justify it.”

This Sunday, 48 states – Hawaii and most of Arizona are the lone exceptions – will “spring forward” their clocks an hour as part of daylight saving time. Clocks will then “fall back” an hour on the first Sunday in November. This cycle – except for a 10-month period in 1974, at the height of the Arab oil embargo – has been ongoing in the U.S. since 1966 and the establishment of the Uniform Time Act. The Energy Policy Act of 2005 added four weeks to daylight saving time by changing its start from April to March.

Today, the U.S. is among only 70 of the 195 countries globally to still observe daylight saving time. While there’s been political movement to the contrary – USA Today reported in November that 19 states, over the past four years, have enacted legislation or passed resolutions to provide year-round daylight saving time – scientists say year-round standard time provides the most health benefits.

“The clock in your brain is synchronized by external cues,” Güler said. “The most important being the sunrise and sunset. And you can interfere with it by other light. That’s why light at night is not a good thing, because it’s mimicking the sunrise. So that information will be taken by your brain and say, ‘OK, adjust your clock accordingly.’”

According to research conducted from 2009-16 at the Bronx’s Montefiore Medical Center, the risk of heart attacks and stroke increases by 24% when clocks go forward in the spring and an extra hour of sleep is lost. That risk then falls by 21% when clocks go back in the fall and that extra hour of sleep is regained.

Güler pointed to a February 2020 edition of Current Biology, a peer-received scientific journal, as the best case for year-round standard time. Among the report’s highlights was a study that revealed 28 fatal accidents could be prevented yearly if daylight saving time was abolished.

“We could save 28 lives,” Güler said.

Provencio leans on the research of Till Roenneberg from the University of Munich. Roenneberg’s report, “Daylight Saving Time and Artificial Time Zones: A Battle Between Biological and Social Times,” argues for perennial standard time because, among a variety of reasons, that best aligns the body with the sun’s clock.

“The transition we go through in the spring is like flying from Chicago to Charlottesville,” Provencio said. “It’s a one-hour transition. And people say, ‘Oh, it’s pretty easy to do,’ but in fact, it’s not exactly the same. The flight from Chicago to Charlottesville, it changes an hour, but when you arrive there, the sun is actually in the proper position for that local time. Whereas when we switch the clock, that’s no longer the case.

“Humans tend to have a clock slightly longer than 24 hours, so that means every day, every cycle, it has to actually be advanced a little bit, right? And when you detect light during the day, that will determine whether or not you delay or advance that clock.

“When the sun hits your eyes, that conveys information to the clock in your brain. When you go over time zones, the new time zone, the sun is still in the correct relative place for the local time, right? If you just switch the clock, then you’ve kind of messed around with that.”

Of course, there’s also a case to be made for perennial daylight saving time. The Department of Transportation cites energy conversation, fewer traffic accidents and drops in crime as daylight saving’s main benefits. A study published in the journal Epidemiology in 2017 observed that transition out of daylight saving time for the year saw an 11% increase in depressive episodes, thought to be caused by disruption of sleep patterns or darker evenings.

“Our body clock, it’s set based on our exposure to sunlight,” said Dr. J. Kim Penberthy, a clinical psychologist in UVA Health’s psychiatry and neurobehavioral sciences department. “So when it’s dark outside, that’s a signal that is sent to our brain to sleep, to rest, to sort of shut down. And obviously in the fall and winter, those days are shorter and our body clock might become disruptive to a lack of exposure to sunlight, and that can lead to more symptoms that we would call seasonal depression.”

UVA Health’s Dr. J. Kim Penberthy says she prepares patients for time changes each year. (Photo courtesy of UVA Health)

One possible solution in the daylight saving time versus standard time debate would be to pick one or the other and get rid of clock changes.

“We could all stay on the same rhythm,” Penberthy said.

But until such change is enacted, people are forced to adjust twice each year. Penberthy said she talks through preparations with her patients each fall and spring.

“In the springtime, if you’re getting seven to eight hours a sleep, go to bed a little earlier the night before the change and try to adjust that so that you’re getting more caught up on your sleep beforehand,” she said. “So you could do something like go to bed 15 to 20 minutes earlier than usual each night and the days leading up to it or even just one night before helps. It helps to recoup some of that sleep.

“Our sleep is a lot like our bank account. You can go into a deficit and one good night’s sleep does not make up for it. So if you have been sleep deprived for a long time and then you hit this daylight saving time and spring forward and lose 40 minutes or so of sleep, that’s adding to your deficit. You’re just going negative and negative and negative, so you really need to think about getting a surplus of sleep. That might mean sleeping a little longer when you can, even if that’s on a weekend.”

Another tip? Invest in light therapy.

“There are these light boxes that mimic the beams from the sun,” Penberthy said. “They don’t burn you – they’re not going to cause a sunburn or anything – but they do promote the same sort of stimulation that sunlight would promote if you were exposed to that.

“A lot of my patients use them, especially in the winter and the fall. They wake up and they get exposure to this light for about 30 minutes. They sit in front of their light and drink their coffee and read their newspaper. So that’s trying to trick your internal clock into believing it’s morning.”