A tired man at a desk rubbing his eyes.

At 2 a.m. Sunday, the clocks in most states across the U.S. will shift forward 1 hour, leaving many of us us feeling sleepy and out of sorts.

One hour of lost shut-eye isn’t really the problem: Time changes can wreak havoc on our internal circadian rhythms—the natural cycles that govern a wide range of the body’s processes.

Suddenly waking up in the dark makes this situation even worse. “Light in the morning helps to set our circadian rhythms,” says Nate Watson, M.D., professor of neurology at the University of Washington and co-director of the UW Medicine Sleep Center. “Right after the time change, we won’t have that natural wake-up cue.”

Most people can adjust to a one-hour time difference within a day or two, but don’t be surprised if you struggle longer.

More on Sleep

Or if your teenager does. With adolescents, “we found that the effect was compounded as the week went on,” says Ana Krieger, M.D., medical director of the Weill Cornell Medical College Center for Sleep Medicine and an author of a study published in the Journal of Clinical Sleep Medicine that looked at how this group adjusts to the onset of daylight saving time, or DST. “The subjects were tired throughout the week, and their reaction times were slower.”

The switch may have other effects as well, some that seem more directly related to sleepiness than others. Overall, although the evidence on whether DST hikes auto accidents is mixed, a study published in the journal Epidemiology in 2018 found that car crashes in New Zealand went up 16 percent the first day after and 12 percent the second day after DST—before leveling off. (About 70 percent of countries have some form of daylight saving time.) 

And some research over the years—including a research review, published in 2018—also suggests that there may be a link between the March time-shift and a small uptick in heart attacks.

Still other studies have found that you might be more likely to miss a medical appointment in the days after DST or to spend more time "cyberloafing"—spending work time on personal emails and visiting websites unrelated to your job.

You will eventually adjust to the new time, of course. But small changes to your routine can help make the transition seamless. 

Tips for an Easy Time Change

  • Go to bed early Saturday night—and avoid the temptation to sleep in. “If you get up at your normal time on Sunday morning, it will make it easier to fall asleep at the correct clock time Sunday night,” says Michael H. Bonnet, Ph.D., professor of neurology at the Wright State Boonshoft School of Medicine in Dayton, Ohio. That way, you won’t lose another hour of sleep Sunday night and be even more sleep-deprived for work on Monday.
  • Expose yourself to bright light as early as possible. Even if the sun’s not up when you get out of bed, get out in the sun as soon as it is. “That exposure to bright light will help nudge the body’s rhythm in the direction it needs to go,” Bonnet says.
  • Skip the afternoon latte. “No coffee after 2 p.m. is a good general rule for better sleep, but it’s even more important while trying to adjust to the time change and thus getting to bed earlier,” Watson says.
  • Don’t schedule early morning meetings this week. “Our brains are still half asleep, and alertness may be kicking in an hour or so later than usual until we adjust,” Krieger says.
  • Take extra care on the road. Though evidence on DST and car crashes is not conclusive, it's wise to take extra care—and to watch out for other sleepy drivers. “The spring clock change means that you’re not the only one who may be feeling less alert behind the wheel,” says Jennifer Stockburger, director of operations at CR’s Auto Test Center. “So it’s important for you not only to do all of the things that keep you most attentive but to remain particularly aware of what’s going on around you, as other drivers are likely in the same boat.”