Daylight Saving Time 101

Learn about how daylight saving time has both benefits and negative consequences.

Days before they head to the polls, most Americans will face something almost as contentious as this year’s presidential race: daylight saving time (often called daylight savings time).

The twice-yearly changing of the clocks (spring forward one hour in spring, fall back one hour in fall) boasts a strange and colorful history including death cheaters, draft dodgers, and a 20th-century superpower that forgot to change the clocks for 60 years.

And recent polls confirm that a growing number of people despise it. This year alone, a dozen U.S. states attempted to end the annual ritual.

“I think the principal annoyance is that it's confusing,” says Tufts University professor Michael Downing, author of Spring Forward: The Annual Madness of Daylight Saving Time.

Yet some interest groups insist that daylight saving time is worth saving.

We’ve compiled the main arguments for and against DST. Take a look and then tell us which side you’re on.

Power Failure

Ben Franklin, with tongue planted firmly in cheek, floated the idea of daylight saving as a way to save money on candles. ("A penny saved …")

But what our illustrious Founding Father suggested in jest became government policy centuries later, when countries started changing clocks to save energy and boost industrial production during the first World War.

More daylight in the evenings means less demand for lights and electricity, the theory goes. But studies from Indiana to Australia have shown that to be an outdated rationale. The advent of central heat and air conditioning means that temperature, not lighting, is the primary driver of energy use. A Department of Energy study of 2007's one-month DST extension showed the event did little to lower the power bill.

“I think the cynicism about [DST] has been fueled by the absolute fallacy of the energy savings that we were meant to be accruing,” says Downing. (Read "Daylight Saving Time's Strange and Surprising History.")

Rhythms and Blues

Scientists have examined DST's impacts on human health, and the conclusions have been mixed. Two studies, conducted in the United States and Sweden, found that heart attack risk increased by up to 25 percent on the Monday after we move the clocks ahead. The same researchers found that the risk dropped by 21 percent when the clocks fall back.

Till Roenneberg, a chronobiologist at Ludwig-Maximilians University in Munich, argues that our bodies' circadian clocks never entirely adjust to the shift in daylight hours. So while more morning light helps jump-start our bodies, the extra evening light leads to a lag.

"The consequence of that is that the majority of the population has drastically decreased productivity, decreased quality of life, increasing susceptibility to illness, and is just plain tired," Roenneberg previously told National Geographic.

Scheduling Problems

Despite the persistent belief that the time change benefits agriculture workers, farmers have often been leaders in the opposition, since it means a shift to schedules for partners like markets and suppliers, and disrupts the habits of livestock unaccustomed to being milked or fed an hour earlier.

In addition, some religious groups—with holy observances based on solar and lunar time—don’t like government mandates meddling with the hour hand. And parents of schoolkids often loathe sending their children off in morning darkness. Even TV networks see an annual 10 to 15 percent drop in viewership during the week after DST begins.

Daylight Dollars

Many businesses tend to support DST for a simple reason: money. Extra hours of evening daylight spur summer spending. That's most obvious with outdoor businesses like golf courses, but others also enjoy a boost simply because more people are out instead of hunkered down at home.

“The retail sectors that continue to benefit by it feel that it's good for American business to have more daylight,” Downing says. “I think that remains the most compelling argument.”

Need proof? The Association for Convenience and Fuel Retailing touts the DST extension among the top accomplishments in its 50 year history, responsible for tens of billions of dollars in increased gas sales since 1986.

People Like Evening Light

Daylight saving time is designed to deliver more sunlight when people are able to enjoy it: in the evening after work and school rather than during the morning rush. But is it appreciated?

In the 1950s and ‘60s, Gallup did a number of surveys that found people tended to favor DST after living with it for a few years. However, recent polls have been mixed. A 2012 Rasmussen Reports telephone poll of a thousand Americans found 45 percent of them thought DST was “worth the hassle” while 40 percent did not. When a different thousand people were asked the same question in 2014, 48 percent responded that DST wasn't worth it, while only a third of those surveyed thought it was worth the hassle.

One group that doesn't like DST at all is the criminal class. A 2015 report by the Brookings Institution found that, on the first day of DST, robbery rates fall by an average of 7 percent. The most recent statistics reveal that the extension of DST saved $59 million in social costs by reducing robberies annually, since late-rising criminals don't shift their activity to morning hours even when it's dark.

Off the Clock

Prior to the U.S. Uniform Time Act of 1966, individual cities were left to decide whether to observe DST and to choose the date on which their clocks changed. (Read "Seven Other Surprising Things You May Not Know About Daylight Savings.")

Still, the system is plagued by chaos. Most African and Asian nations skip daylight saving time while most North American and European nations observe it—half the planet is out of sync with the other.

In the U.S., states are free to debate the issue, since the federal government doesn’t require them to follow the time change. Hawaii, Arizona (except the Navajo Nation), and a handful of U.S. territories don’t bother with DST.

This summer a Massachusetts economic development bill established a commission to look into putting the state permanently in the Atlantic time zone with Canadian provinces New Brunswick and Nova Scotia. If the idea to shorten evenings of winter darkness goes anywhere, it would likely include other states so that New England could change time zones as a region, says health advocate Tom Emswiler who originally authored the bill.

On the country's other coast, California's state senate killed a bill in August that would have given voters a ballot option to eliminate the observance of daylight saving. Those same voters, or their grandparents, originally approved California DST in 1947.

“This year, as usual, there were more than a dozen states where individual bills were at least in the hopper to either abandon the project altogether, or to go on full-year DST,” Downing notes.

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