Millions of Americans will lose an hour's sleep Saturday night, as daylight savings time returns. Officially clocks should be moved ahead one hour at 2 a.m. Sunday, but most people will change their clocks before going to bed Saturday night. The lost hour will return October 29 when clocks fall back to standard time. Congress has passed a law changing the dates of daylight-saving time, from March 11 to November 4, but that doesn't take effect until 2007.