ATOMIC CLOCKS HOW THEY WORK
Sets Itself: Atomic Clock
This Sharp Atomic clock automatically synchronizes itself to the US Governments National Institute of Standards and Technology in Fort Collins, Colorado. The WWVB radio signal daily broadcast ensures that the atomic clock will always display the most accurate date and time.
In most areas, a signal can only be received at night. If your clock does not receive the WWVB signal immediately, just wait overnight and it should be set in the morning. It may take up to 48 hours.