Casio's atomic and atomic-solar watches represent revolutionary time-keeping technology. That means no more worries of changing the time on your watch when you're within the U.S.! These watches all feature atomic timekeeping powered by Casio waveceptor technologyand, in some cases, even solar power. The built-in solar technology eliminates the worries of replacing batteries, and the atomic function means minimizing the worry of having to reset the time during Daylight Saving Time.