It’s Time to Change the Clocks Again. Why Do We Do This to Ourselves?

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In the wee hours of the morning on Sunday, clocks in most of United States will fall back, marking the bittersweet end to Daylight Time that every year inspires feelings of relief and dread: On the one hand, many Americans will enjoy an extra hour of sleep. On the other, the sun will start setting before all but the earliest of early-bird specials.

Most Americans don’t like this confusing and disruptive ritual of changing our clocks twice a year. But they’re split about which side of the system they prefer. In March, a bipartisan group of senators reintroduced a bill to get rid of Standard Time and make Daylight Time permanent, following the lead of 19 states that have passed similar legislation. But others — scientists who study sleep and biological rhythms, especially — argue that it’s Daylight Time that should be scrapped. Here’s a look at the debate.

Why do we change our clocks in the first place?

The origins of Daylight Time are often traced back to Benjamin Franklin, who in a 1784 satirical essay suggested that the city of Paris could save millions of pounds of candle wax every year if Parisians woke up earlier in the morning and went to bed earlier at night.

It wasn’t until World War I, though, that the idea gained serious political momentum. In 1916, the German government embraced moving the clocks forward as a means of saving energy. “While the British were talking about it year after year, the Germans decided to do it more or less by fiat,” David Prerau, author of “Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time,” explained to National Geographic in 2019.

Soon, England and much of the rest of Europe followed suit, as did the United States. In March of 1918, Congress enacted the Standard Time Act, which both defined the country’s time zones and temporarily instituted the clock change. The change was initially unpopular, however, and wouldn’t become permanent until the Uniform Time Act of 1966, which established Daylight Time throughout most of the country. (Arizona and Hawaii remain holdout states.)

While the division between the two time systems was equal at first, Daylight Time has over the decades come to rule a bigger and bigger share of the year. Today, Standard Time is in effect now for only about four months, between November and March.

The twice-yearly switch no longer saves much energy, but it does take a serious toll on people’s health. “Light is the most powerful regulator of our internal clock, also known as our circadian rhythm, and some people may not even adjust to the time change after several months,” says Anita Shelgikar, an associate professor of sleep medicine and neurology at the University of Michigan Health System. “Chronic misalignment between the internal clock and occupational, family and social activities can be very disruptive.”

In fact, in part because of sleep disruptions — which are particularly acute during the switch to Daylight Time, when people lose an hour of sleep — the transition has been linked to higher heart attack risk, more workplace injuries and more car-accident deaths. In the week after the spring clock change, fatal car accidents increase by 6 percent, according to a study published last year.

Parents also have special reason to dread the transitions, which tend to upend the napping and bedtime routines of young children.

The case for making Daylight Time permanent

If Americans already spend most of the year on Daylight Time, should we just get rid of Standard Time altogether, as so many legislators have proposed?

Steve Calandrillo, a law professor at the University of Washington who has conducted economic research on the topic, thinks it’s the right move. One reason is that darkness in the evening is associated with both larger numbers of fatal car accidents and higher levels of crime than darkness in the morning.

“D.S.T. brings an extra hour of sunlight into the evening to mitigate those risks,” he writes. “Standard Time has precisely the opposite impact, by moving sunlight into the morning.”

Businesses have historically been some of the most vocal champions of Daylight Time. When there’s more light in the evening, the theory goes, consumers will use it to leave their homes and spend their money. In 1986, lobbyists for the golf industry estimated that an extra month of Daylight Time would be worth $200 million to $400 million.

The actual effect may be small, but still significant: A report from the JP Morgan Chase Institute found that consumers spend 0.9 percent more at the onset of Daylight Time and 3.5 percent less in the month after the clocks fall back.

Proponents of Daylight Time also argue that having more daylight in the evenings is simply more useful — and less depressing. According to a 2017 study, the transition from Daylight Time to Standard Time is associated with an 11 percent increase in depressive episodes, an effect that takes 10 weeks to dissipate. The spring switch, by contrast, was found to have no similar effect.

Getting rid of Standard Time “would mean you would sometimes wake up with it slightly darker outside, but you’d get so much more sunlight and ‘daytime’ after 5 p.m.,” Ben Yakas wrote for Gothamist in 2019. “Ask yourself if you are more likely to be outside in the world at 7:30 a.m. or at 5:30 p.m., and then you’ll know where you really fall on this issue.”

The case against Daylight Time

While extending summer hours into the winter may sound appealing, manyscientific organizations, including the American Academy of Sleep Medicine, say Standard Time is actually better overall for people’s health.

That’s because Standard Time — once called “God’s Time” by farmers who objected to the 20th-century adoption of Daylight Time — allows for closer alignment of the sun’s light-dark cycle, which governs our circadian rhythms, and our social clocks, which dictate, among other things, when people need to wake up for work and for school.

“Believe it or not, having light in the morning actually not only makes you feel more alert but helps you go to bed at the right time at night,” Beth Malow, director of the sleep division of Vanderbilt’s School of Medicine, told Kaiser Health News last year.

When social clocks are out of alignment with the solar clock, people experience what’s called “social jet lag.” AsErin Flynn-Evans and Cassie Hilditch wrote for the Society for Research on Biological Rhythms last year, there is mounting evidence that social jet lag has serious health effects, including short sleep duration, increased metabolic disorders, cardiovascular problems, mood disorders and even reduced life expectancy and increased risk of cancer.

The effect of social jet lag is so pronounced, the two researchers noted, that even “Individuals who live on the western side of a time zone, where there is more sunlight in the evening, have a higher risk of poor health and shorter life expectancy compared to those who live on the eastern side, where the sun rises and sets earlier relative to the clock time.”

By pushing the sunrise later into the morning hours, Daylight Time exacerbates social jet lag, Joseph Takahashi, the chair of the neuroscience department at the University of Texas Southwestern Medical Center, told my colleague Jane Coaston on this week’s episode of “The Argument.”

“So if we went to permanent Daylight Saving Time, we would have additional months of this non-optimal phasing of our clocks, and that could lead to even higher incidence of cancer than we currently see in the United States,” he said. “I would say that’s the most compelling reason for why we should not adopt Daylight Saving Time because cancer, as you know, is the second major cause of death in the United States.”

As it happens, a plurality of Americans agree with Takahashi: 40 percent believe we should adopt Standard Time all year, according to a 2019 poll, compared with 31 percent who believe we should make Daylight Time permanent.

Both camps outnumber the 28 percent of Americans who prefer switching back and forth. But for now, at least, time is on their side.

Do you have a point of view we missed? Email us at [email protected]. Please note your name, age and location in your response, which may be included in the next newsletter.


“Daylight Saving Time Should Be Permanent. The Pandemic Shows Us Why.” [Time]

“Why Should We Abolish Daylight Saving Time?” [Journal of Biological Rhythms]

“Who wants to go to work in the dark?” [University of California, Los Angeles]

“Make daylight saving time permanent: Senators Patty Murray and Marco Rubio” [USA Today]

“Why standard time is better”[Medium]

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