Daylight time begins in most of the United States on the second Sunday in March. That's this weekend. Radio station operations are reminded of the clock change in the early hours of Sunday, for their scheduling and other event time-based systems — and because they lose an hour of sleep. Clocks are set ahead one hour at 2 a.m. local standard time, which becomes 3 a.m. local daylight time. We switch back on Nov. 1.