What Is Daylight Saving Time, Anyway?

Photograph by Lisa Poole, AP

Daylight saving time ends for most of the U.S. on November 1. But why do we change our clocks by one hour in the spring in the first place? “In the early 19th century … localities set their own time,” said Bill Mosley, a public affairs officer at the U.S. Department of Transportation. There was no standardized time until train travel became common. The U.S. railroad industry established time zones with standard times in 1883, and Congress made the railroad’s system a law in 1918. The next year, the decision of whether or not to observe daylight saving time was left up to individual jurisdictions.

Some places, like American Samoa, Hawaii and most of Arizona, don’t mess with Father Time. For those places that do observe it, though, the law says that people must set their clocks back to standard time at 2:00 a.m. on the first Sunday in November. This Sunday, the sun will set an hour earlier. The switch to daylight saving time again on the second Sunday in March “adjust[s] daylight hours to when most people are awake and about,” Mosley said. During daylight saving time months, there’s less light in the morning and more light in the evening. Although more light in the evening isn’t helpful to everyone (like farmers), research shows that longer daylight hours decrease traffic accidents and crimes.

When updating legislation in the 1980s, Congress noted that daylight saving time has many benefits, including “more daylight outdoor playtime for the children and youth of our Nation.”

Read more about daylight saving time on National Geographic News.

Read about atomic clocks on National Geographic News.

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