The Radio Controlled Clock
This LaCrosse Technologies Radio Controlled clock uses an onboard receiver to communicate with a WWVB
VLF (very low frequency) radio transmitter operating at 60 KHz by the National Institute of Standards and Technology in Fort Collins, Colorado.
Because of the low frequency, reception at my location is limited to the overnight hours but the quartz movement of the clock maintains accuracy between nightly "updates".
Sometimes advertised as an "atomic clock", it is, instead, linked with the actual NIST Cesium atomic clock in Boulder, Colorado and displays time within about 0.02 seconds accuracy.