Daylight Saving Time begins in U.S.

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WASHINGTON, March 10 (UPI) -- Daylight Saving Time started at 2 a.m. Sunday, giving those who observe the time change an extra hour of daylight in the evenings.

Most Americans sprang forward an hour in time early Sunday, losing an hour of sleep, but gaining an hour of sunlight at the end of the day, ABC News reported.

DST was first used in World War I to conserve resources and then again during World War II until Sept. 1945. Then, the Uniform Time Act of 1966 created a standardized system to observe daylight saving time.

In 2007, Congress adjusted the start time of DST to begin the second Sunday of March and run until the first Sunday of November. Previously DST started in mid-April and was observed until October

Not all U.S. states and territories observe the time shift; Arizona, with the exception of the Navajo Nation in the northeastern part of the state, does not participate in Daylight Saving Time, neither do Hawaii, American Samoa, Guam, Puerto Rico, Northern Marianas and the Virgin Islands.

The U.S. Department of Transportation says the extra daylight has led to less traffic accidents and reduced crime because "people travel to and from school and work and complete errands during the daylight," and "more people are out conducting their affairs during the daylight rather than at night, when more crime occurs."

However, researchers in Sweden have found that the time change can have a negative impact on the body.

"More than 1.5 billion men and women are exposed to the transitions involved in Daylight Saving Time: turning clocks forward by an hour in the spring and backward by an hour in the autumn," wrote Imre Janszky and Rickard Ljung, health and welfare researchers in Sweden. "These transitions can disrupt chronobiologic rhythms and influence the duration and quality of sleep, and the effect lasts for several days after the shifts."