The Atomic Clock has a built-in receiver that automatically synchronizes itself with the WWVB radio broadcast by the US Government's National Institute of Standards and Technology (NIST) in Fort Collins, Colorado. This Silver Atomic Clock will always be accurate to within on second as it receives daily WWVB updates. The compatible with Sharp (SPC569) Color Calendar and Day of Week Display - Always know what day of the week it is with a quick glance. The Digital clock displays the calendar and the day of the week. Using the Snooze/Dimmer switch on top of the display, you can easily adjust the display brightness to your liking. Atomic Color Alarm Clock – Accurate to the Second! Perfect for nightstand or bedside table! The Atomic Clock has a built-in receiver that automatically synchronizes itself with the WWVB radio broadcast by the US Government’s National Institute of Standards and Technology (NIST) in Fort Collins, Colorado. The Atomic Clock will always be accurate to within on second as it receives daily WWVB updates. The compatible with Sharp (SPC569) Color Calendar and Day of Week Display - Always know what day of the week it is with a quick glance. The clock displays the calendar and the day of the week. Using the Snooze/Dimmer switch on top of the display, you can easily adjust the display brightness to your liking. Color Atomic Alarm Clock - Accurate to the Second! The Atomic Clock has a built in receiver that automatically synchronizes itself with the WWVB radio broadcast by the US Government’s National Institute of Standards and Technology (NIST) in Fort Collins, Colorado. The Atomic Clock will always be accurate to within on second as it receives daily WWVB updates. Color Calendar and Day of Week Display - Always know what day of the week it is with a quick glance. The clock displays the calendar and day of the week. Using the Snooze/Dimmer switch on top of the display, you can easily adjust the the display brightness to your liking. EASY TO SET DUAL ALARM - Set alarm for two people, or set one alarm for weekdays and the other for weekend!. Snooze/Dimmer Switch is simple to use and on top of the display. BATTERY BACK-UP - There is a "No Worry" battery back-up option (requires 2 x AAA battery, sold separately), that will allow the alarm to go off, even if the power goes out. The battery back-up stores the time and alarm settings if the power is interrupted. During battery back-up the clock’s display will not be lit. Once power is restored, the display will re-light.