Clock changes can throw you for a loop. Even a one-hour shift, as happened in most of the US on Sunday, can leave you feeling groggy and out of sync for days. That’s because your body’s internal clock—your circadian rhythm—relies on daylight, meal times, and a steady routine. When the country’s twice-yearly time change comes along, it disrupts that rhythm and leaves your body playing catch-up.
The good news is that with a few simple habits, you can help your body bounce back quickly and reset your sleep schedule naturally after a time change. Follow these tips to get back in the groove and start feeling like yourself again after those clocks turn.
What Is Daylight Saving Time?
In the US, most of the country switches between standard time and daylight saving time (DST) in November and March. Standard time is the “normal” clock time used in the fall and winter, while DST is the one-hour shift in spring and summer that shifts daylight from morning to evening.
Each year, clocks spring forward one hour in March, and we lose an hour of sleep. The clocks then fall back in November, giving us that hour back. The idea is to maximize daylight hours for work and play in the warmer months.
Daylight saving time started during World War I as a way to save energy. More daylight in the evening meant less need for artificial lighting, which was in short supply at the time. It was also thought to help farmers by giving them extra daylight in the evening. However, since farm work follows the sun, not the clock, it mostly just made their schedules trickier.
More than a century later, most Americans still follow the same ritual. Exceptions include Hawaii and most of Arizona, where plenty of daylight and desert heat make the time shift more of a hassle than a help.
Why Time Changes Mess With Your Body Clock
We tend to focus on how long we sleep, but consistency is just as important, says Rebecca Robbins, a sleep researcher at Brigham and Women’s Hospital and Harvard Medical School. “Just as important as sleep duration, if not more, is consistency of sleep schedules,” she says. “Changing by even one hour can be enough to throw our internal circuitry off.”
Your circadian rhythm relies on cues like lights, meals, and routine. Light is ultra-important here, as it suppresses melatonin, the hormone that tells your brain it’s bedtime. When daylight shifts, so do your hormones.
That rhythm conducts far more than fatigue. It regulates digestion, alertness, mood, and even immune response. When you spring forward, you’re essentially forcing your body’s clock out of sync with your environment. Falling back is gentler, since the extra hour of sleep and morning light usually help your rhythm adjust more easily.
Health Costs of Losing Sleep
The impact of time shifts can show up almost immediately. “Car accidents, heart attacks, cardiovascular sequela, mood disorders—all these things tend to stay elevated throughout the duration of being on daylight saving time,” says neurologist and sleep specialist W. Chris Winter at Charlottesville Neurology and Sleep Medicine. A study from the University of Colorado found that fatal car crashes in the US spike by about 6 percent in the week following the spring shift to DST.
Most Americans are already running on a sleep deficit. “Only 30 percent of Americans report consistently meeting their biological need for sleep,” Robbins says. A lost hour compounds that debt.
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