Every November, you experience time travel and jet lag without getting on an airplane or, of course, actually time traveling. That's right, the first Sunday in November marks the end of daylight saving time, when much of the Western world turns its clocks back by one hour to return to standard time.
In the days that follow, you might find yourself asking: Why do I feel more tired or lethargic than usual, and how do I get back to normal? We're here to help.
Despite its history of good intentions, the effects of daylight saving time have serious biological implications that have inspired more and more people to ask the question: Is it time to do away with daylight saving time?
In this article, we’ll examine the origins of and growing objections to daylight saving time and discuss how shifting our clocks just one hour in the fall can have outsize effects on sleep, health, and public safety. Even when you gain an hour in the fall, the time change itself as well as the shorter days of winter can lead to sleep debt and circadian misalignment. We’ll also share tips on how to plan for the autumn transition to minimize sleep loss and how to use good sleep hygiene to keep your sleep and energy on track during the wintertime.
The idea behind daylight saving time (DST) is to have darkness fall at a later clock time during the spring and summer, which gives people an extra hour of daylight while the weather is warm.
In the United States, DST starts on the second Sunday in March, when we “spring forward” by setting our clocks one hour ahead of standard time. It ends on the first Sunday in November as we “fall back” by setting our clocks back one hour to standard time.
Over the past century, more than 140 countries across the globe have implemented it at some point, but today, less than 80 countries — mostly in the West — observe DST.
Even the United States has some abstainers. Hawaii and Arizona (except for Navajo Nation) do not observe daylight saving time, nor do Puerto Rico, Guam, American Samoa, the Northern Mariana Islands, or the U.S. Virgin Islands. To the north, by contrast, Canada’s Saskatchewan and Yukon provinces have adopted year-round DST.
You might think of daylight saving time’s one-hour time change as a simple fact of life. Like paying taxes, it’s just something we do every year, like it or not. However, daylight saving time is actually a relatively new development.
Some people credit Benjamin Franklin for inventing daylight saving time. But in reality, his suggestion — in a satirical letter published in the Journal de Paris in 1784 — that Parisians could economize the use of candles and lamp oil by getting out of bed earlier in the morning was given in jest.
The modern concept of daylight saving time was actually the brainchild of New Zealand entomologist George Hudson. In 1895, he came up with the idea for a two-hour time shift in the summer that would give him more daylight to go bug hunting after work.
The first real use of DST didn’t come until 1916 when parts of Germany — and later other European countries — set clocks ahead one hour for energy-saving purposes during World War I. In 1918, a similar tactic was used in the United States, but only for a few months. During World War II, President Franklin Roosevelt revived and rebranded the seasonal time shift as “War Time,” which lasted from 1942 to 1945. After that, decisions related to daylight saving time were left to the states and local municipalities, which led to growing confusion for radio and TV stations, transportation companies, and the like.
Finally, in 1966, congress passed the Uniform Time Act establishing the last Sunday in April as the start of daylight saving time for the whole country and the last Sunday in October as the end. States could opt out of this nationwide policy by passing a state law.
In 1986, the federal government moved the start date of DST up to the first Sunday in April, and with the Energy Policy Act of 2005, further extended the DST to its current length: from the second Sunday in March to the first Sunday in November.
Historically, this twice-yearly one-hour change in local time has been seen as benign. But is it?
The body experiences time change as a kind of jet lag. When your internal clock suddenly doesn’t line up with the numbers on the clocks around you, circadian misalignment can become a real problem.
Your circadian rhythm is an internal body clock that governs your sleep-wake cycle and other energy fluctuations in roughly 24-hour periods. Keeping a consistent sleep schedule that lines up with your circadian rhythm makes it easier to get the sleep your body needs.
The twice-yearly time changes associated with daylight saving time can throw off your circadian rhythm and make it harder to get sufficient sleep, which can lead to sleep debt.
Sleep debt is the amount of sleep you missed — as compared to the hours of sleep your body needed — over the past 14 days. Because it’s the number that best predicts how you feel and perform on any given day, sleep debt is the main focus of the RISE app. In order to feel good and perform at or near your best, we recommend keeping your sleep debt under five hours.
Although ostensibly we lose only one hour of sleep on the second Saturday in March as DST goes into effect, studies show that we’re more likely to have difficulty falling asleep and/or staying asleep and experience a cumulative sleep loss over the next seven days. And it can take four weeks or longer for our bodies to adjust to the time change. Even with the fall time change, when we supposedly “gain” an hour of sleep, it’s not uncommon to experience a net sleep loss over the next week (more on this later).
According to Matt Walker, the author of “Why We Sleep,” these shifts in and out of DST are a “global experiment” that proves even one-hour changes in the sleep you get on a single night can have drastic impacts.
To understand why a twice-yearly time change can be so disruptive, let’s look at the different “clocks” involved:
Because light is the primary cue for your circadian rhythm, experiencing gradual internal shifts in your body clock — as the days get longer or shorter with the changing seasons — is normal. Your body clock is simply reflecting changes in the sun clock. This is how circadian cues are supposed to work.
But with DST time changes, when the social clock suddenly shifts our schedules by a whole hour overnight, it actually throws off your body clock’s relationship to the social clock by weeks in terms of the natural seasonal changes of the body clock.
When a sudden manmade change in the social clock throws your circadian rhythm out of whack and simultaneously disrupts your sleep schedule, it’s easy to see how your sleep can be negatively impacted.
Studies show that a mere one-hour shift in circadian timing — from daylight savings time changes or sleeping later on weekends than you do on weekdays — can increase subjective sleepiness and significantly downgrade reaction time performance.
The negative effects of daylight saving time changes often ripple out into bigger problems for public health and public safety. In addition to increases in traffic accidents and fatal car accidents, researchers report a higher incidence of workplace injuries in the days immediately following the start of daylight saving time in March.
We also see an uptick in cardiovascular and neurology-related risks. A nine-year study by researchers at the University of Turku in Finland reported that the risk of ischemic stroke increased on the Monday and Tuesday following the start of daylight saving time in March.
And a 2013 study published by the American College of Cardiology found a 25% increased risk of heart attack on the Monday after the start of DST in the spring.
While these studies and statistics don’t show a causal relationship between DST time changes and extreme negative health effects, they do highlight the importance and fragility of our sleep health. It begs the question: If a one-hour change in sleep time is enough to hasten a heart attack in someone with heart problems, what other perhaps undetected health issues are being exacerbated by daylight saving time?
On the flip side of these scary statistics, in the days following the change back to standard time in the fall, incidences of stroke, heart attack, and traffic accidents fall to below normal levels. It’s like seeing in real time — and on a large scale — the incredible benefits of catching up on sleep.
Are you an early bird or a night owl? Your chronotype indicates whether you are genetically predisposed to an early bedtime and wake time or a later bedtime and wake time.
As it turns out, early birds have an easier time adjusting to the “spring forward” time change. But it’s not so easy for night owls, as it can take up to eight weeks for their sleep to return to normal!
Interestingly, there seems to be less difference in the ways the early and late chronotypes handle the “fall back” time change, although there’s some evidence that indicates the fall transition is more challenging for early birds, who wind up getting less morning light.
Do you feel more alert and in a better mood in the week after DST ends in November? Turns out there’s research to support the validity of those improvements. The autumn time change can also help you experience what it feels like to pay down debt without even trying. Those good feelings might inspire you to make getting enough sleep a priority moving forward.
Because you’re gaining an hour of sleep, the November shift out of DST is easier to adapt to as compared to the March shift into DST. But it’s still important to be smart about the transition.
Without preparation (transitioning in advance), it can take up to two weeks to adjust to the November time change, depending on how often you have to use an alarm clock to wake up for work, school, or other obligations. You might be able to adjust your sleep in just one week on free days, but it can take up to two weeks on work days.
Here are some ideas for a smooth transition into the November time change.
Reducing or keeping your sleep debt low going into the autumn time change will make the transition easier. People who habitually short themselves on sleep are at a big disadvantage when it comes to adjusting to DST time changes.
If you want to prepare for the autumn time change to mitigate social jet lag, you can start the week before by moving your bedtime and wake time back by 15 minutes until the end of DST on the first Sunday in November.
Because we’re setting our clocks back an hour, the first Sunday in November is a golden opportunity to pay down sleep debt. But research shows that most people don’t take full advantage of it, getting on average only about 40 minutes of extra sleep. It’s important to try to get the full hour to make up for the sleep you’ll likely lose during the days following the time change. While sleep loss when you’ve gained an hour may seem paradoxical, it is due to an increase in spontaneous awakenings as well as earlier rise times as your body adjusts.
Focusing on your circadian rhythm and sleep hygiene is especially important as DST ends and through the winter months.
Sleep hygiene refers to the upkeep of behaviors that influence the way you sleep. From being careful about the timing of your caffeine and alcohol consumption to taking time to wind down at night and keeping your bedroom cool, dark, and quiet — your daily habits have a big impact on your sleep. So think about stepping up your sleep hygiene routine in preparation for DST time changes.
Because darkness prompts the body to produce the sleep-inducing hormone melatonin, and light is a signal to stop that production, it’s important to be strategic about the timing of your light exposure. It’s a vital part of good sleep hygiene, and it’s especially crucial during the winter months. Shorter days and less bright sunlight (at latitudes more than 30 degrees north or south of the equator, which includes almost all of the United States) can throw off the timing of our normal sleep/wake cycle, affecting our energy levels.
Exposing yourself to light in the morning and daytime is always important for sleep, but especially during the shorter, colder days. Spending more time indoors means you’re likely exposed to much more electric light both during the day (which is too dim) and at night (which is then too bright).
So make a point of getting sunlight on your skin in the first 30 minutes after waking, and avoid or dim indoor electric light — or wear blue light-blocking glasses — in the 90 minutes before bed.
And to support the body’s natural drop in body temperature in preparation for sleep, resist the temptation to pile on more blankets or wear extra layers of bedclothes in winter. A cool bedroom (65-68 degrees) is ideal for sleep.
It’s not uncommon to have difficulty adjusting to seasonal changes, especially going into fall and winter. And about 5% of Americans suffer from seasonal affective disorder (SAD), a type of recurring wintertime depression that challenges sleep and can last four to five months.
Scientists don't know definitively what causes SAD. But one theory is that the sufferer’s circadian rhythm reacts more slowly to light cues, making it less effective at regulating the body’s melatonin and serotonin, which affect sleep and mood.
To feel your best during winter, try these coping strategies.
In the words of University of Michigan neuroscientist and geneticist Margit Burmeister, Ph.D., “DST makes everything worse for no good reason.”
Indeed, the negative effects of the twice-yearly government-mandated time changes are hard to ignore.
The American Academy of Sleep Medicine recently issued an official statement that made clear its recommendation that the United States should eliminate seasonal time changes: “Current evidence best supports the adoption of year-round standard time, which aligns best with human circadian biology and provides distinct benefits for public health and safety.”
A number of lawmakers across the country want to eliminate the spring and fall time changes as well. State legislatures in New York, Maine, Ohio, Minnesota, Oregon, and Florida have introduced bills, and in some cases passed laws, to put their states on permanent daylight saving time year-round. However, these laws cannot take effect under the current federal law that allows states to stick with standard time all year, but not daylight saving time.
In March 2021, a bipartisan coalition submitted a bill called the Sunshine Protection Act of 2021 for consideration in the U.S. Senate. It would make DST the permanent, year-round time so that Americans would no longer have to deal with changing their clocks and compromising their sleep health two times every year. The bill has to make its way through the House, Senate, and President before it goes into law.
If there’s one thing we can learn from all of the research and findings on the effects of daylight saving time, it’s how pivotal and fragile our sleep schedules are. When we see the dramatic negative impacts of shifting our social clocks “just one hour” every six months, we may start to question the sleep-disrupting changes we bring often upon ourselves. From personal and professional obligations to bedtime procrastination, shift work, and travel across time zones — skimping on sleep and throwing your circadian rhythm a curveball can have serious consequences.
It’s hard to ignore the deleterious effects of DST time changes, but for now, most of us will have to make the best of a less-than-ideal situation. Being especially strategic about your fall and winter light exposure — and maintaining overall good sleep hygiene — is your best bet for getting your sleep and circadian rhythm back to normal after we set our clocks back in the fall.
And Rise can help. Use the RISE app to help you get to know your circadian energy schedule, keep track of your sleep debt, and stick to your sleep hygiene habits and routine. Because no matter what the season, getting the sleep your body needs is the key to better days.
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