Atomic Clock/Never Needs Setting, Digital Wall Clock with Indoor Outdoor Temperature & Humidity, Battery Operated, Wireless Outdoor Sensor, Atomic Wall Clock with 4.5" Numbers Easy-To-ReadACCURATE ATOMIC CLOCK: The atomic clock has a built in receiver that automatically synchronizes itself with the WWVB radio broadcast by the US Governments National Institute (NIST) in Fort Collins, Colorado. Digital wall clock adjusts time & calendar to atomic signal automatically, and could count seconds accurately. (Note: no backlight display) 15" LCD HIGH DEFINITION DISPLAY: The Atomic Clock has a 9. 4 inch tall upgraded LCD high definition display