The United States and other areas observing both standard and daylight savings time turn the clocks back on the first Sunday of November at 2:00 a.m. Prior to 2007, the change traditionally took place on the last Sunday of October at 2:00 a.m.
Turning the clock back an hour returns the time to the standard time for that particular zone. The area then observes standard time until the second Sunday of March when daylight savings time begins and clocks are moved forward. Because observation of seasonal daylight savings time is not a law, some American states and territories choose to opt out of changing the time. Hawaii and most of Arizona do not observe daylight savings time. Time changes in the United States date back as far as 1918.