Been longing for that extra hour of sleep? Your chance arrives this weekend, as Daylight Saving Time officially ends. Most of the U.S. (except Arizona and Hawaii) will fall back an hour to Standard Time at 2 a.m. Sunday morning.

If those extra hours of daylight seem to stick around longer than they did when you were a kid, there’s a good reason for that.

Until 2007, when the Energy Policy Act of 2005 was put into effect, Daylight Saving Time began on the first Sunday in April and ended on the last Sunday in October.

Daylight Saving now begins on the second Sunday in March and ends on the first Sunday in November.

Caution should be used by both motorists and pedestrians as shorter days arrive. A 2003 study by researchers at Stanford and Johns Hopkins universities analyzed a 21-year period and found a significant increase in traffic accidents on the Sunday ending DST.

Extra care is encouraged for the first several days following the time change. Commuters who have worked a full day have to deal with dark roads and end-of-day exhaustion, a potential recipe for disaster.

In another study by researchers at Carnegie Mellon University, the risk of pedestrian fatalities (per mile walked) jumped 186 percent after DST ends, before dropping 21 percent on average in December.

There is good news concerning the fall time change, however. The rate of heart attacks falls by five percent the first three workdays after DST ends.