The radio controlled clock, often called an atomic clock, has become very popular in recent years. Today, an atomic digital clock is relatively inexpensive, often costing just a few dollars more than conventional clocks. Radio controlled clocks are available in all forms: atomic wall clocks, desk clocks, travel alarms, wristwatches, and even atomic weather stations! They have a tremendous advantage over conventional clocks since they are always right, and it's great to have at least one atomic clock in your home or office.

A radio controlled clock is accurate to within a second and never needs to be adjusted. They can even self-adjust to daylight savings time (DST) and back again when standard time is in effect. Radio controlled clocks are commonly referred to as "atomic clocks," but that isn’t technically true. A real atomic clock has an atomic oscillator inside (such as a rubidium or cesium oscillator). A radio controlled clock contains a relatively simple antenna and radio, which receives an atomic clock synchronization signal that is transmitted from a place where the atomic clock is located.

In the United States and Canada, a radio controlled clock synchronizes on at least a daily basis (typically at night) with the cesium time base atomic clock located at the National Institute of Standards and Technology (NIST), Time and Frequency Division in Boulder, Colorado. The powerful NIST transmitter, WWVB, transmits its atomic clock synchronization signal over 2000 miles and is generally available throughout North America.