First, the name. It is daylight saving time, singular, though nearly everyone says “savings.” And it does not save daylight at all. Moving the clocks forward an hour just shifts when we are awake relative to the sun, spending more daylight in the evening and less in the morning.
How we got the current schedule
The U.S. used daylight saving time during both world wars, and the Uniform Time Act of 1966 standardized it nationally while letting states opt out. Hawaii and most of Arizona do. The Energy Policy Act of 2005 extended it, starting in 2007, so that it now runs from the second Sunday in March to the first Sunday in November, several weeks longer than before.
Does it save energy?
That was the main argument for the extension. When the Department of Energy studied the change, it found the extra weeks cut electricity use by about 0.5 percent per day during the extended period, which worked out to roughly 0.03 percent of the country’s electricity use for the year. Other studies have found the savings small or nonexistent, partly because evening air conditioning and morning heating use can cancel out lighting savings.
The costs
The spring switch costs people an hour of sleep, and researchers have linked the days after it to small increases in heart attacks and car accidents. The American Academy of Sleep Medicine has argued for ending the switch in favor of permanent standard time, which it says better matches the body’s clock.
The stalemate
Many people agree on ending the twice-a-year change but disagree on which time to keep. In March 2022 the U.S. Senate passed the Sunshine Protection Act by unanimous consent, which would have made daylight saving time permanent, but the House did not take it up. Dozens of states have passed laws to adopt permanent daylight time if Congress allows it. Federal law currently lets states choose permanent standard time but not permanent daylight time. Until Congress acts, the clocks keep changing.
Sources: Impact of Extended Daylight Saving Time on National Energy Consumption, U.S. Department of Energy; Daylight saving time position statement, American Academy of Sleep Medicine; Sunshine Protection Act, Wikipedia; Daylight Saving Time, U.S. Department of Transportation.
