What daylight saving time does to your body

How to best prepare for time change
How to best prepare for time change

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  • Although the time change adds an extra hour of sleep, it can be jarring for the body
  • Don't stay up late, even though it feels like you can

This autumn, daylight saving time has us "falling back" — or gaining an hour of sleep — during the wee hours of Sunday, November 1. While that may sound like the perfect way to recover from a weekend of Halloween fetes (or candy comas), it can be surprisingly jarring on the body.

"The time change is kind of a society-imposed jet lag," says Dr. Ilene Rosen, who serves on the board of directors for the American Academy of Sleep Medicine (AASM) and is board-certified in sleep medicine. Here's how to re-acclimate by Monday morning.

    What Is Daylight Saving Time?

    The time shown on the clock from November to March is known in the Northern hemisphere as "standard time." The rest of the year is considered the exception, or "saving time." Countries in the Southern hemisphere, however, reverse this, observing daylight saving time during their summer — between November and March.
    Making matters even more confusing, daylight saving time (DST) isn't practiced everywhere in the world. Most of Asia and Africa as well as parts of Australia and South America don't observe DST at all — nor do Hawaii, Arizona, or many US territories, like Guam and the US Virgin Islands. (Utah may also consider dropping DST, based on public outcry.) Even where it is practiced, clocks are set forward and back on different dates, leading to even more regional variations.

    Why Do We Have It?

    If you live in a part of the world that experiences wide shifts in weather and daylight hours between summer and winter, you probably relish any extra time you get to spend outdoors in the summer sunshine. Moving the clock forward an hour in the spring gives people an extra hour of daylight in the evening, when they're typically not working, rather than the morning. Added bonus for night owls: It also moves the sunrise an hour later, keeping late-risers' bedrooms conveniently dim.
    It's not clear, though, whether all this inconvenience is worth it. One hundred years ago, when DST was first introduced in war-torn Germany, there was a case to be made for saving energy. Moving the clock forward in the spring reduces the number of waking hours between sunset and bedtime (since bedtime remains static while sunset occurs an hour later, according to the clock). Fewer post-sunset evening hours ought to mean fewer lights turned on, and less money spent on energy.
    Newer studies throw this hypothesis into question, though. When DST was introduced, lightbulbs were the primary use of household electricity. These days, we use our TVs, computers and other small appliances just as much, whether it's light or dark out. Meanwhile, lightbulbs have grown more efficient. And now that we live in a world where we can control indoor temperature (phew!), it's possible that having more waking daylight hours could, in fact, increase our energy use, since air conditioning uses so much more power than a few measly lightbulbs and is typically turned higher during daylight hours. Studies are inconclusive, but even if it does save money, the savings are estimated to be no more than one or two percent.

    How to Deal

    In a perfect world, DST wouldn't shock our circadian rhythms twice annually. "Ideally we would be able to allow our internal circadian rhythms to move along naturally with the light-dark cycles that change from season to season," says Dr. Rosen. Since that's not possible, try these tips to transition back to standard time with ease.

    1. Don't Stay Up Late

    When you set the clocks back each fall, "your circadian rhythms will cause you to want to go to bed earlier and wake up earlier than your external environment," says Dr. Rosen. "One of the biggest mistakes that people make ... is staying up later and thinking that they're going to get an extra hour of sleep," she adds. Because your circadian rhythms may wake you early Sunday morning, it's important not to count on that extra snooze time.

    2. Use the Sun

    The fall time change is easier than the spring, says Dr. Rosen, particularly for those who work standard daylight hours, since you're able to hack your sunlight exposure. Try to get as much late afternoon sun exposure before switching the clocks back, and as much morning sun exposure as possible after switching the clocks to help ease the transition.

    3. Take Your Time

    "If you work a non-traditional schedule, or have a little extra time in the morning, it might ease the transition if you go to sleep and wake up 10-15 minutes later each day the week before the time change," says Dr. Rosen. As always, adding a nap can help fend off drowsiness for anyone still struggling with the switch back to standard time