Atomic Alarm Clock Offers Worldwide Accuracy Accurate to the nanosecond, this atomic clock automatically syncs to one of the World Time Clocks in North America, the U.K., continental Europe or Japan, ensuring reliable time when you travel. When you’re outside signal range, just set the clock, calendar and alarm manually. Features a unique twist-and-turn base, snooze function, backlight and travel pouch. Uses two CR2450 batteries (included). Plastic. Imported. Global Atomic Alarm Clock2 3/4″W x 1 3/4″D x 3 3/4″H. 4.4 oz.