Cyberguys Ken-Tech Home Office School Decorative Large Digital Atomic Alarm Clock Accurate to 1 second every 60 million years, the atomic clock signal is broadcast all over North America by the National Institute of Standards and Technology. With a large-sized numbers, built-in alarm clock and atomic precision, this elegant digital atomic clock can be mounted to a wall or set on a desk. The easy-to-read display indicates not only the time, but also the date and the day of the week. Requires 1 AA battery, not included. Radio-controlled "atomic clocks" set themselves automatically by tapping into the time signal broadcast from a cesium fountain atomic clock located in Boulder, Colorado. Accurate to 1 second every 60 million years