With the exception of Arizona, Hawaii and the territories of Puerto Rico, Virgin Islands, Guam and American Samoa, at 2 a.m. on Sunday, March 9, Americans will turn their clocks forward one hour, marking the beginning of Daylight Saving Time (DST).

The federal law that established "daylight time" in the United States does not require any area to observe daylight saving time. But if a state chooses to observe DST, it must follow the starting and ending dates set by the law. From 1986 to 2006, this was the first Sunday in April to the last Sunday in October, but starting in 2007, it is observed from the second Sunday in March to the first Sunday in November, adding about a month to daylight saving time.