This digital wall clock displays a.m./p.m. or 24-hour time. It also displays month, date, day of the week and ambient temperature in °F and °C. It is visible from 20 ft. away and has 2½ in.-high digits. It adjusts to daylight saving time; a radio signal from N.I.S.T. in Colorado automatically adjusts the clock to precise time, daylight saving time, leap year and leap seconds (earth rotation wobble corrections). It comes with wall mount, screw and two AA batteries. A certificate is provided to indicate instrument traceability to standards provided by N.I.S.T. Calibrated by an ISO/IEC 17025 calibration laboratory accredited by A2LA.