In the United States Daylight Saving Time begins at 2:00 a.m. local time on the second Sunday in March. On the first Sunday in November areas on Daylight Saving Time return to Standard Time at 2:00 a.m. When Daylight Saving Time begins, turn your clocks ahead one hour. At the end of Daylight Saving Time turn your clocks back one hour. For most Americans, Daylight Saving Time means only one thing: losing an hour's sleep. So what is the point? This is actually a reasonable question, according to a growing body of scientific research. Most of North America and Europe follows Daylight Saving Time, while the majority of countries elsewhere do not. When clocks in almost all of the United States spring forward by an hour at 2 a.m. on Sunday, it will likely prompt an increase in heart attacks and strokes, cause more car accidents and reduce worker productivity, according to studies. It will also fail to cut the nation's energy bill, contrary to what the experts once believed. Disruptions, even minor ones, to human beings' sleep patterns can have outsized effects, according to researchers. "Our study suggests that sudden, even small changes in sleep could have detrimental effects," Amneet Sandhu of the University of Colorado told Reuters in 2014 after his study of Michigan hospital data showed a 25 percent jump in heart attacks on the Monday after Daylight Saving Time began. Daylight Saving Time, which runs until the fall, was widely adopted during World War Two as an energy-saving measure. The rationale was that a later sunset meant people would spend fewer hours using lights inside their homes in the evening. But studies have generally failed to show significant energy savings associated with the shift. Plenty of people expressed frustration on social media on Saturday, as the prospect of losing an hour's sleep loomed large. Abolishing Daylight Saving Time – or conversely, extending it year-round – would require a law passed by U.S. Congress. States are allowed to opt out of Daylight Saving Time, but all states are required to follow standard time from November to March. Legislators in some states have tried unsuccessfully to pass laws abandoning Daylight Saving Time, but Arizona and Hawaii are the only states that do not reset their clocks twice a year. For everyone else, Sunday morning will come just a little bit earlier than usual.