Round wall clock is radio-controlled so the setting is modified each day to that of the atomic clock, accurate to one second per million years. The clock automatically adjusts to Daylight Saving Time and designed to work in the continental United States. Design also features an easy-to-read white dial, black Arabic numerals and tempered glass cover. Clock runs on one AA battery (sold separately).Round wall clock is radio-controlled so the setting is modified each day to that of the atomic clock, accurate to one second per million years. The clock automatically adjusts to Daylight Saving Time and designed to work in the continental United States. Design also features an easy-to-read white dial, black Arabic numerals and tempered glass cover. Clock runs on one AA battery (sold separately).