What is an Atomic Watch?

R. Kayne

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.

Keeping an atomic watch in a safe may block the watch's ability to find a signal.
Keeping an atomic watch in a safe may block the watch's ability to find a signal.

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.

Being too close to power lines may affect an atomic watch's ability to find a signal.
Being too close to power lines may affect an atomic watch's ability to find a signal.

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.
An atomic watch has a different mode setting for each time zone.

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.

Initially, atomic watches were digital with plastic sports-style casings.
Initially, atomic watches were digital with plastic sports-style casings.

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!

Traditional clocks and watches use a system of gears and pulleys to keep time.
Traditional clocks and watches use a system of gears and pulleys to keep time.

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Discussion Comments


Since daylight savings time started my atomic watch is not keeping correct time. I have tried to set it manually with no luck.


I work nights and I sleep during the days. I bought the watch and it was fully charged. One week later it became uncharged even though I was allowing it to be in my window during the days. I got it to charge at the middle position. but it seems to be a fight since I wear it at night with low light levels. How do I charge it better working at night? Does casio make one with a regular battery? I really like the feature with the correct time but now half of the functions are not working. any suggestions


When the watch resets itself, if it is not a digital watch, do the hands actually turn to the correct time?


I live in Venezuela. Does this watch recive this signal in here?


As an Atomic Watch is solely a receiver, it only makes sense that such a watch would not be directly detrimental to the operation of nearby medical equipment. While anything with electricity running through it will have some amount of an Electro Magnetic Field, that which your watch battery would normally be able to generate would be negligible & though that field would be greater than the field produced by the magnetic strip in a credit card or many modern driver's licenses, but smaller than the field around a refrigerator magnet. The concerns would come from the natural coverage of the many natural or low probability (static electricity, lightning, solar flares, synthesized thermonuclear detonations, . . .) & commercial radio waves being broadcast 24 hours a day, which, if hospitals have anything to be truly concerned about, either the hospital or the medical equipment manufacturer would have to take, or to have taken, steps to shield against possible common malign effects, or even somewhat unusual imaginable effects. Which means that hospitals do not require & request that cell phones not be used around the many devices that lives can hang in the balance over if these medical devices do not operate perfectly, but they do require & request our commitment to their rules because of the rare possibility that a malfunctioning communication device could malfunction in a catastrophic way during a text message or idyllic rant & kill grandma, a risk that they calculatedly take with the operation of the many medical devices within the hospital, that are also subject to the rare possibility of a catastrophic failure that could emit a burst of electro magnetic energy that could then possibly disrupt grandpa's pacemaker, the Monty Python machine that goes ping, or the operation of the robotic arm on the microsurgery unit in Surgical Room 2. With that much risk already inherent in the system that is meant to keep people alive, they do not want to add any additional risk to the equation by allowing non-essential operation of fallible devices that have nothing to do with actual hospital operations, but then who among us would want to even think that there was a tiny, infinitesimal possibility that the woman in the next room over might have died because we had been conducting even important business with our office or babysitter while visiting a sick friend at the hospital. If the business was that important, the ethical thing to do is to step out of the hospital to the parking lot or further & then make that cell phone call.


Your hospital is concerned about the transmission of radio waves that would be transmitted from a radio transmitter such as a cell phone. It is possible for radio waves transmitted from a cell phone to interfere with medical equipment/devices.

Let's clarify what an atomic watch does. An atomic watch contains a small antenna which receives data from a transmitter in Ft. Collins Colorado. The watch itself does not transmit anything harmful. There is nothing to be concerned about. I hope this helps.


The hospital where I work is very fussy about cell phone and microwave usage. Does the low-frequency radio wave reception by the watch have any potential impact on medical devices?

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