A radio controlled clock or "Atomic Clock" keeps near perfect time by automatically synchronizing to the radio signal emitted from the U.S. Atomic Clock in Colorado. Radio controled clocks reset daily to the split second, and adjust automatically to Daylight Savings Time, Leap Year and Time Zone Changes.
NIST distributes time-of-day and frequency information to the public using radio broadcasts. The low frequency (LF) station WWVB is located in Fort Collins, Colorado and broadcasts on 60 kHz. The high frequency (HF) stations WWV and WWVH are located in Colorado and Hawaii respectively, and broadcast on five different frequencies ranging from 2.5 to 20 MHz. At least one HF signal should always be usable at any given time anywhere in the United States.