An atomic watch is a wristwatch that is radio controlled to keep the most accurate time on earth. You never need to set the time or date of an atomic watch because it receives a low-frequency radio signal nightly that keeps it in perfect synchronization with the U.S. Atomic Clock in Colorado.
An atomic watch is handy because it automatically adjusts for Daylight Saving Time (DST), often mispronounced as Daylight Savings Time, leap years and even leap seconds. It contains an internal antenna and program that is set to search once a day for the 60 kHz radio signal emitted from the WWVB transmitter in Ft. Collins. When it finds the signal it decodes the time then sets itself. The Ft. Collins transmitter has a radius of 1,864 miles (3,000 km), making it available to the most of the United States with the exception of Hawaii and Alaska.
If you travel overseas with an atomic watch, it will continue to function as a quartz watch but will not receive radio controlled updates. Although Europe has its own atomic clocks, the transmitter frequency used in Europe differs from the one used in the United States.
An atomic watch has a different mode setting for each time zone. When the watch receives the radio signal from the atomic clock, it also reads its internal program that stores the time zone setting. It then translates the atomic time to the proper time zone. Therefore, if you travel to another time zone, you may have to manually change the time zone setting of the watch. For the atomic watch to know the time zone automatically, it would require integrated GPS.
Many atomic watches have a feature that allows you to see when it was last synchronized. You may also be able to manually tell it to search for the radio signal; otherwise the watch is usually programmed to look for the signal in the middle of the night when radio interference is at a minimum.
Certain factors might block the ability for an atomic watch to find the signal on any given night, such as being in a building with excessive shielding, keeping the watch in a safe, laying it next to electronic equipment that emits interference, or being too close to power lines. The watch should continue to look for the signal each night, however, so even if it only synchronizes twice weekly it will still be running very accurately.
The National Institute of Standards and Technology (NIST) is responsible for the NIST-F1 Cesium Fountain Atomic Clock in Ft. Collins that is used by most atomic watches. The NIST-F1 keeps such precise time that it has been mathematically calculated to be accurate to within less than 1 second every 30 million years! Unlike previous clocks that relied on quartz oscillations to time a true second, the atomic clock is based on quantum mechanical principles and is part of an international group of atomic clocks that keep universal time.
An atomic watch can be battery or solar powered. Since the watch usually has no stem for manually setting the time, after a battery change the watch will not display the proper time until it finds the radio signal and sets itself. If you manually initiate it to search for the signal, this could occur within minutes, or if it cannot find the signal it could take up to a few days to start displaying the proper time again.
Initially, atomic watches were digital with plastic sports-style casings, but analog watches with stainless steel cases are also available. Watches are relatively inexpensive and are widely available. They are also referred to as radio control watches or wave receptor watches. If you require or appreciate accurate time, there is no watch more accurate than an atomic watch!