Atomic clocks are known for their amazing accuracy. In fact, they lose only one second every 20 million years. The On-Time Atomic Watch uses the radioactive element cesium (Cs) to set itself using a radio broadcast from the atomic clock. This type of watch rarely needs to be reset, but when it does, it's fairly easy to do.

Press and hold the center button of on the watch for approximately six seconds to change time zones. Your watch should already be set to your time zone when it is sent to you, but if it is set to the wrong time zone or you are traveling, you can use this method to set it. After you press and hold the center button, the second hand will move to the 12:00 position. It will then move to another hour mark, depending on the time zone that you are in.

Press the lower button once and then release to set your watch ahead one hour. To set the watch back one hour, press the upper button once and then release it. If you need to move the watch multiple hours ahead and behind, press the appropriate button as many times as you need.

Press the center button once more when you have finished setting the time with the upper and lower buttons. The second hand will move to 9:00 or 3:00. Press the center button once more and set the watch down. Your watch may take up to 20 minutes to finish resetting itself.