The hands of the Atomic Clock instantly move to exact time. The Traceable® Clock automatically sets itself and is accurate to 1/10,000 of a second. Clock receives a radio signal directly from NIST's atomic clock in Boulder, Colorado. It adjusts for daylight saving time and leaps seconds (earth rotation wobble corrections). Bright second sweep hand is highly visible. To assure accuracy an individually serial-numbered Traceable® Certificate is provided from the manufacturer’s ISO 17025 calibration laboratory accredited by A2LA. It indicates traceability to standards provided by NIST (National Institute of Standards and Technology). Complete with wall mount, screw, and AA battery. Diameter is 12 inches, depth is 1- 1/4 inches. Weight is 1-3/8 pounds. Replacement battery Cat. No. CON1111.