Daylight saving time is a plan in which clocks are set one hour ahead of standard time for a certain period, so that darkness comes an hour later. The plan provides an additional hour of daylight in the evening. Most of the states of the United States observe daylight saving time. Wherever it is observed in the United States, it begins on the first Sunday in April and ends on the last Sunday in October. A state may decide to remain on standard time. States that lie in more than one time zone may use daylight time in one zone and not the other.
Contributor: Joanne Petrie, J.D., Senior Attorney, Department of Transportation.