Standards: Daylight Saving Time (DST)

Daylight Saving Time (DST) is a widely used system that adjusts the official local time forward from the official standard time during summer months, usually by one hour.

• The Uniform Time Act of 1966 provides guidance for selecting the dates when DST begins and ends in the U.S.
• The Energy Policy Act of 2005 established the current DST schedule. As of 2007, DST begins in the U.S. on the second Sunday in March and ends on the first Sunday in November.
• Congress can revert to the previous DST schedule if the current dates do not help save energy. The U.S. Department of Energy (DOE) is studying the impact of the new dates.

The Uniform Time Act also lets states, territories, and tribal areas decide if they will observe DST. Arizona (except the Navajo Indian Reservation), Hawaii , American Samoa , Guam , the Northern Mariana Islands , Puerto Rico , and the U.S. Virgin Islands do not observe DST.

Additional Resources:

• Countries Observing DST
• Daylight Saving Time Rules
• Time Exhibits
• Standards: Leap Year
• Standards: The Seasons