Yes, it's daylight saving time again. As with the return of the swallows to San Juan Capistrano or the blossoming of cherry trees in Washington, D.C., Americans look forward each year to that springtime ritual -- turning their clocks ahead one hour.

Umm, OK, so maybe daylight saving time, which starts 2 a.m. local time Sunday, isn't greeted with the same kind of enthusiasm as those other events, but most people do enjoy that extra hour of sunlight in the evening. Beyond the convenience of, say, being able to fire up the barbecue after a long day at work, however, what purpose does shoving the nation's clocks ahead 60 minutes each spring serve?

For most of its life, daylight saving time has been implemented to reduce energy consumption. As author David Prerau explained to NPR in an interview last year, daylight saving time was put in place by countries on both sides in World War I to save energy, with the U.S. adopting it in 1918.

The time shift was repealed after the war ended, but returned during World War II for the same reasons, said Prerau, author of Seize the Daylight: The Curious and Contentious Story of Daylight Saving Time. In the 1950s and '60s, no national law governing daylight saving time existed, leaving municipalities and states to implement their own rules, resulting in a confusing patchwork of time shifting. Prerau noted the curious case of a 35-mile stretch of highway running from West Virginia to Ohio that required changing one's watch seven times along its route to maintain the correct time, since some towns honored daylight saving time and some didn't.

The Energy Crisis Renewed Interest

The energy crises of the 1970s brought renewed interest in daylight saving time, and a federal law governing its use has existed since. Though Uncle Sam doesn't mandate daylight saving time, states that choose to observe it must follow starting and end dates set by law. Until 2007, daylight saving time began in early April and ended in late October. That year, however, the law was revised, and daylight saving time now begins on the second Sunday in March and ends on the first Sunday in November. The shift added about a month to daylight saving time.

Beyond the annoyance of losing an hour of sleep each spring, experts also say moving clocks ahead may also leave people drowsy. The time switch makes it harder for many to rise in the morning, lessening the ability to stay alert and increasing the chance of accidents during morning commutes.

"Even one hour of sleep loss can affect some people," says Dr. Ronald Chervin, professor of neurology at the University of Michigan and director of its Sleep Disorders Center. More people have serious crashes in the days immediately following the spring change in time, Chervin says, likely attributable to sleep loss and adjustments the body's own clock has yet to fully make to a new schedule.

Preparing for the Daylight-Saving Switch

Still, it is possible for workers, students and others with pressing schedules to prepare for the daylight-saving time switch, Chervin says. It can be as simple as going to sleep and waking up earlier by 15-minute intervals in the days leading up to Sunday's change.

Though it's hard to find any aspect of health that's not altered by lack of sleep, whether a one-hour gain in sunlight in the evening helps reduce energy consumption is still debatable. One expert argues that daylight saving time actually increases gasoline consumption, since Americans spend the additional daylight in their cars going shopping or running other errands.

We can't help but wonder if the drowsiness many will feel Monday won't lead to additional consumption of another valuable national commodity: Coffee. Or if your tastes happen to mesh with the latest manifestation in third-party politics -- tea.

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