While both types of solar watch use solar panels for power, a regular solar watch requires manual time-setting. Conversely, an atomic solar watch sets its time by using a radio signal obtained from the atomic clock found in Fort Collins, Colorado at the National Institute of Standards and Technology. It isn’t magic, but it is still pretty cool.
With no battery and automatic time, the atomic watch is perhaps the most hassle-free watch available. Many solar power watch brands offer both atomic and non-atomic solar-powered watches.