Atomic Clocks are synchronized by signals from the atomic clock in Colorado. Adjust for Daylight Saving Time. Never need resetting! Wall Clock in dome shape has high visibility with 10" face. Mantel Clock with cherry wood finish is 19" x 2" x 8 1/2". Giant LCD features 2" tall time, seconds, date, day; 9" x 9" x 1". Bedside Clock has time, date, month, temperature, alarm; 5" x 2" x 4 1/8". Clocks use AA batteries, not included.