Daylight saving time: Fall back this Sunday Published Nov. 4, 2021 By DLA Public Affairs FORT BELVOIR, Va. -- Daylight saving time begins the second Sunday in March and ends the first Sunday in November, when clocks are adjusted one hour back to standard time. The United States adopted daylight saving time when the Uniform Time Act of 1966 standardized time zones and daylight saving practices across the United States. The act allowed states to pass laws exempting themselves. The only states that don’t observe daylight saving time are Hawaii and most of Arizona. It’s also not observed by these U.S. territories: American Somoa, Guam, Puerto Rico and the Virgin Islands. Also, it's recommended to use this time to change batteries in smoke detectors and other home safety devices. The National Fire Alarm and Signaling Code requires that a working smoke detector be installed in and outside every room used for sleeping, as well as on every level of the home including the basement. Homes that use wood or natural gas for fuel should also have a least one carbon monoxide detector.