The history of daylight saving time and its effect on our health

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This weekend, nearly all of us will set our clocks back one hour. It's part of the twice-a-year ritual of alternating between daylight saving time and standard time. William Brangham looks at the history of changing the clock and a movement to do away with this process, once and for all.

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  • Judy Woodruff:

    This weekend, nearly all of us will set our clocks back one hour as part of the twice-a-year ritual of alternating between daylight saving time and standard time.

    But, as William Brangham reports, there's a movement under way to do away with this process once and for all.

  • William Brangham:

    Like almost all of us in the country, Scott Yates is about to set his clocks back one hour, as we do every fall when the nation falls back to standard time.

    But Yates, like a growing number of Americans, is sick of it.

  • Scott Yates, Lock The Clock:

    You know, if somebody snuck into your house and changed your alarm clock, so it went off an hour earlier than your body was expecting, you would be so mad.

  • William Brangham:


  • Scott Yates:

    And yet the government does it. Every year, we're all so sleep-deprived, we don't really know how to respond.

  • William Brangham:

    In every state except Arizona and Hawaii, clocks spring forward in early March to start daylight saving time and fall back in early November to begin standard time.

    A few years ago, Yates' wife said, stop complaining about it and do something. So, he started a blog compiling various studies and reports about why we change our clocks, what the economic impacts are, even some pretty striking evidence that this back-and-forth switching can harm people's health.

  • Scott Yates:

    You can compare, what's the heart attack data on the Monday after the spring forward time change in places that do have the change and in places that don't have the change, like Arizona, and they don't have a spike in heart attacks on that Monday morning after in Arizona, and they do everywhere else.

    And so it becomes really pretty clear evidence.

    It's really just kind of a glitch in the way that we operate the clocks, and it's a deadly glitch.

  • William Brangham:

    Yates became something of a go-to expert, testifying before different state legislatures.

  • Scott Yates:

    My name is Scott Yates.

  • William Brangham:

    Even trying an unsuccessful run for Congress in his home state of Colorado, all focused on this issue of stopping the biannual change.

    It's an idea that is gaining popularity. In the last few years. 19 states have passed legislation to do away with the switch and make daylight saving time permanent, even though federal law prohibits states from doing that.

    But then, earlier this year, in the Senate, the bipartisan Sunshine Protection Act was introduced. It would make daylight saving time permanent starting next year.

  • Sen. Edward Markey (D-MA):

    So, daylight saving time brings sunshine, smiles and savings.

  • Sen. Marco Rubio (R-FL):

    I have watched sporting events be called, youth sporting events be called in the middle or near the end of the game before it's actually concluded because there's not enough lights.

  • Sen. Patty Murray (D-WA):

    Any parent who has worked so hard to get a newborn or a toddler on a regular sleeping schedule understands the absolute chaos changing our clocks creates, and for no good reason.

  • William Brangham:

    The Senate unanimously passed the bill in March, but it's stuck in the House over debate on which time, daylight or standard, is the one to lock our clocks on.

    So, if there is this groundswell to stop switching, why do we even do it in the first place?

    Where did this idea come from that I remember being told as a kid that this was to help the farmers of America?

  • David Prerau, Daylight Saving Historian:

    That is one of the myths that I don't understand about, because it's 100 percent wrong, 100 percent wrong.

  • William Brangham:

    David Prerau has written two books on the strange history of why we change our clocks. He also worked in the federal Department of Transportation, helping craft this policy in the 1970s.

    During World War I, the Germans changed their clocks to preserve energy during the summer months. And, in 1918, the U.S. tried the same and kept it up through both World Wars.

  • David Prerau:

    Not only, by the way, did it save energy, but it did other things. Like, it left an extra hour in the evening when people can come home from work and tend to victory gardens, which would grow — grow some food extra for the war effort.

  • William Brangham:

    For the next few decades, cities and states could choose what to do with their own clocks. But, in the '60s, President Johnson signed a law setting specific dates for daylight saving time. It said, if states chose to do it, it had to be statewide.

    Richard Nixon, Former President of the United States: In the short term, we face a problem.

  • William Brangham:

    Then, in the early 70s, trying to ease an energy crisis, President Nixon signed a law which locked the clocks on daylight saving time year-round.

    But, pretty soon, Americans saw the darker side to daylight saving, which adds more sunshine to the evening, but takes it from the morning.

  • David Prerau:

    What happened was, it seemed OK until the middle of winter in 1974, when it became very unpopular very quickly. People really disliked the winter daylight saving time. They disliked having to get up in the pitch dark, having to commute to work in the dark, and having to send their kids to school in the dark.

  • William Brangham:

    President Ford then reversed course, and we went back to changing clocks twice a year, which brings us to today and this movement to go back to permanent daylight saving time.

    According to one poll earlier this year, nearly six in 10 Americans want to ditch the switching. While that could mean longer days in the fall and winter, giving us more light to enjoy the great outdoors — it's partly why the golf industry supports the move — some health experts say, not so fast.

  • Dr. Beth Malow, Vanderbilt Medical Center:

    Waking up in the pitch black is not normal for our bodies.

  • William Brangham:

    Beth Malow is a pediatric neurologist at Vanderbilt Medical Center. She says, yes, later, sunsets are great, but stealing that morning light can have real detrimental effects.

  • Dr. Beth Malow:

    Morning light is key in terms of helping people have a normal, healthy sleep cycle and be able to get to bed at night.

  • William Brangham:

    So the light that you're exposed to in the morning can not just have an effect on you in the morning, but it can have an effect 12, 14, 16 hours later on your sleep?

  • Dr. Beth Malow:


    I wish, in an ideal world, we could have light at both ends. But if we have to choose where to get our light, where's the most healthy part of the day to get our light, it's actually in the mornings, for the reasons I mentioned, because it helps us synchronize our bodies and our brains to what's going on in our environment.

  • William Brangham:

    She argues that, on balance, if we have to pick one option only, permanent standard time would be the healthiest option.

    After his years of studying the issue, David Prerau argues for keeping the current system and helping people manage the transitions better.

    He says, remember, permanent daylight saving gives you sunnier evenings, but much darker mornings.

  • David Prerau:

    You would have mornings — for example, in places like New York, Chicago, Dallas, Denver, San Francisco, the sun would rise at 8:30.

    In places like Detroit, Indianapolis, Minneapolis, Seattle, the sun would rise at 9:00 a.m. So, if the sun is rising at 8:30 or 9:00, almost everybody is going to work and to school in the dark. That's a pretty big negative a lot of people didn't like. And they didn't like it in 1974.

  • William Brangham:

    So, while Congress and state legislatures debate the issue, we can all enjoy a couple more of these long autumn evenings before Sunday morning, when we fall back into darkness.

    For the "PBS NewsHour," I'm William Brangham in Washington, D.C.

  • Judy Woodruff:

    And this is far too controversial a question for me to express my own opinion.

    Thank you, William.

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