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Atomic Clock Synch

What To Do When The Time Displayed Is Wrong

Atomic digital clocks works great, as is evident by the hundreds of thousands of units that have been sold throughout the United States. There is never a need to check an atomic radio controlled clock that is working properly, which is the great thing about how an atomic clock works. They should always display the correct time. However if a problem with atomic clock synchronization is suspected, the clock should first be checked by using the NIST atomic clock on the internet or by listening to NIST radio station WWV using a shortwave radio or telephone (dial 303-499-7111). If this check confirms the radio controlled clock isn't displaying the correct time, the following general tips may be helpful in correcting the problem. Please be sure to save the clock's instruction manual in case future reference is necessary.


Minutes and seconds are the same in all time zones, only hours are different. If the atomic radio controlled clock is off by one or more hours, it probably has to do with the time zone setting. Make sure the time zone has been properly selected using the instructions that came with the clock.

Some atomic digital clocks only allow the selection of four different time zones (Pacific, Mountain, Central, and Eastern). Other atomic wall clocks may allow the selection of any time zone, even time zones that are outside the WWVB coverage area. When purchasing a clock, make sure that it can display the correct time zone.


Make sure that DST is disabled in areas that do not observe Daylight Saving Time (Arizona, Hawaii, parts of Indiana). Not all atomic digital clocks have this feature and another time zone may have to be selected in order to make the clock display the correct time when DST is in effect.

If Daylight Saving Time went into effect and the atomic radio controlled clock didn't change, first make sure DST is enabled (check the instructions). If DST is enabled, it's likely due to a reception problem, i.e. the radio controlled clock doesn't know about the time change. If uncertain that the WWVB atomic clock signal is being received, see the tips for improving reception on our atomic clock synchronization page.


If an atomic radio controlled clock isn't currently receiving the WWVB atomic clock synch signal, it's time display will gradually “drift” away from the correct time. The clock is no longer radio controlled; it's just a regular quartz clock. Quartz clock accuracy depends on the quality of the quartz crystal. Most are accurate to one second per day or better, but some could be off by several seconds per day. If uncertain that the WWVB atomic clock synch signal is being received, see our improving reception tips (atomic clock synchronization).

If you have an analog atomic radio controlled clock, it's possible that the hands aren't properly aligned. This could cause the clock to be off by a second or more even if it is receiving the atomic clock synch signal properly. The clock might not have been properly aligned at the factory, or it might have been jostled during shipment, causing the hands to move. A hand alignment adjustment procedure may be provided in the instruction manual. When checking an analog radio controlled clock, be sure to look straight at the clock face and not from an angle, since the hands may appear to be off by a few seconds even though they are not (like trying to read a speedometer from the passenger seat of a car, thinking the speed is faster or slower than it actually is).

All content on the WeatherShack Education Center is Copyright 2002-2020 This material may not be reproduced, displayed, modified or distributed without the express prior written permission of For permission, please contact [email protected].

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