Juan Moyano/Stocksy Every second Sunday in March marks the start of daylight saving time (DST), the annual period of the year the clocks are shifted one hour ahead. In 2021, DST officially starts at 2 a.m. on Sunday, March 14. Jumping the clock forward and back to standard time every year was designed as a way to optimize daylight hours, which supposedly nets energy savings, prevents traffic accidents, and reduces crime, according to the U.S. Department of Transportation. But for those who live in states that practice DST (Arizona and Hawaii are the only U.S. states that don’t), research is increasingly showing that the annual time change can actually have unintended detrimental consequences to health.