|La Crosse Technology radio controlled Atomic Clocks are the most accurate you can own. Simply push time zone selection (EST, CST, MST, PST), insert one AA alkaline battery (not included), hang it on the wall, and your clock will do the rest. It will automatically set the hour, minute, and second hand to the exact time for your time zone and will stay accurate for the life of the battery (2-3 years). Receives time signal from National Institute of Standards and Technology Atomic Clock. Adjusts automatically to daylight savings time. Features internal antenna and manual time setting.