Why daylight saving is so hard on the body — and what to do about it

Twice a year, Americans shift the clock — an hour forward in the spring, an hour back in the fall — in a well-known practice known as daylight saving. Originally introduced during World War I as a means of conserving fuel and power by extending the amount of daylight each day, the tradition has persisted in some capacity since 1966. This year, most of the country (except for Hawaii, Arizona, and Alaska) shifts from standard time — which runs from early November through mid-March — to daylight saving time on Sunday, March 10.

The premise is simple: shift the clocks so people can get the maximum amount of daylight. In the spring, the one-hour change means more daylight in the evening and darker mornings; in the fall, the sun sets earlier while mornings are lighter. But this transition can be more disruptive beyond just losing one hour of sleep. Whether you’re a parent (to humans or pets) or an early riser who hardly enjoys waking in the dark, you can make the transition into daylight saving a little less painful.

“It’s not just a loss of an hour asleep, but we’re getting our light at a whole different time of day,” says Beth Malow, the director of the Vanderbilt Sleep Division at Vanderbilt University Medical Center. “Everything is off by an hour.”

Every process within the body, from sleep to metabolism, runs on an internal clock, known as circadian rhythm. Various cues, like light, trigger the release of hormones alerting the body to wake up, feel sleepy, get hungry. Even if you wake at the same time every day, the shift from standard to daylight saving time means it’s suddenly dark in the morning and your circadian rhythm is disrupted. “The body releases sleep-time and wake-time hormones at a particular time,” says Nilong Vyas, a board-certified pediatric sleep coach, founder of family sleep consulting service Sleepless in NOLA, and medical reviewer for SleepFoundation.org. “When the clock time is different than what the body is feeling or experiencing, we tend to feel a bit off until the body’s hormones re-regulate in a few days.”

Compared to the gradual change in daylight hours leading up to daylight saving time, the abrupt shift is a jolt to the body. All of a sudden, you’re eating, sleeping, and socializing at different times, and the body needs to play catchup. This sudden change has material impacts: Studies have shown that deadly car accidents, workplace injuries, and heart attacks increase following the springtime change.

Usually, people who work during the day and have consistent schedules can adjust within a week, says Jade Wu, author of Hello Sleep: The Science and Art of Overcoming Insomnia Without Medications. Those on the western edges of time zones see later sunrises than people on the eastern areas of time zones, which may make the adjustment more difficult, Malow says, since it’s darker longer in the morning.

Some people are more sensitive to the time change than others. Older people, people with autism, and adolescents may have more difficulty adjusting, Malow says. Genetics can play a role as well. Young children, pets, and others who aren’t aware of the time change are also thrown out of whack.

In the name of consistency, in 2022, the Senate unanimously voted in favor of making daylight saving time permanent starting in 2023. This would mean eliminating the “fall back” time change in November (and every other hour shift thereafter). Most of the country would experience sunsets after 5 pm — but later sunrises, too (it would be dark at 7 am most of the year). The bill died in the House, but was reintroduced in the Senate in 2023 and has not advanced this year. The bill would need to be passed by the Senate, House, and signed by the president to become law.

For those who enjoy more light in the evening, the move toward permanent daylight saving time is ideal, but it may not be the best for human functioning. Between standard time and daylight saving time, Malow has a preference for standard time. “It’s a healthier choice,” she says, because mornings are lighter during standard time. “We know that morning light is really important for our sleep and our moods,” she says. “Light in the afternoon isn’t as effective as light in the morning. If you want people to have natural light, you want them to have more light in the morning and that’s what standard time does.”

Since the country is stuck with daylight saving time for the foreseeable future, there are ways to ease into the time change. In the weeks leading up to daylight saving time, prioritize your sleep, Malow says, and make sure you’re not sleep deprived before losing an hour of sleep. (The necessary number of hours of sleep varies from person to person, but the CDC recommends adults get between seven and nine hours a night.)

Then, try to go to bed 10 to 15 minutes earlier each night the week before the time changes. “A 10-minute shift is a lot less of a jolt to the system than an hour,” Malow says. But if you’re not sleepy enough for an advanced bedtime, prioritize waking up 10 to 15 minutes earlier, Wu says, since you can more easily control when you rise, not when you fall asleep.

Parents can implement this subtle change in their children’s sleep schedules as well. If they’re resistant to waking up earlier, don’t worry, Wu says — they’ll adjust on their own. “Kids tend to be morning people anyway,” she says. “If the clock shifts one hour, it doesn’t really mess with them that much because they’re still getting up early.” For teens, who are natural night owls and are often sleep deprived, Wu advises parents to guide their teenagers toward less screen time at night and a long wind-down time prior to bed. “If you can, try your best to plan for at least eight hours of sleep knowing that you’re gonna have to wake up at X hour in the morning in the new time,” Wu says.

While infants and pets who aren’t as regimented with their sleep might not be as amenable to a change in when they wake up, parents (to both humans and pets) should still acclimate themselves to a slightly earlier bedtime for an easier transition. Try feeding your pets a few minutes ahead of schedule each day leading up to daylight saving time so they’ll be properly adjusted.

On Sunday morning, fight the urge to sleep in an hour later to compensate for the lost time — wake up around the same time you usually do on Sunday mornings, Malow says. If you typically attend a 9 am yoga class or religious service, keep those plans. Try to get outside in the morning, too, “because that will also reset your clock,” Malow says. Get the family together and go for a walk to ensure everyone gets their dose of daylight. If you have a sunrise alarm clock or a light box, these artificial light sources are also sufficient sources of light and can help get your circadian rhythm back on track, Vyas says.

“The remedy,” Vyas says, “is to ease into the time change so that it is not as jarring for the body when it happens.”

Update, March 8, 2024: This story, originally published March 8, 2023, has been updated for the current year.