10/01/2026
How do radio-controlled watches actually set themselves?
On the left is my Citizen AT9070-51L with the H820 movement. On the right is my JDM Seiko SBTM293 with the 7B75.
Different brands. Different movements. Yet those seconds hands are ticking together almost perfectly.
The answer is WWVB—a 60 kHz time signal broadcast from Fort Collins, Colorado. Each watch independently receives the same time information and uses it to correct itself.
They’re not talking to each other. They’re just listening to the same clock.
Pretty incredible technology hiding inside two otherwise normal-looking watches.
WatchCollector Horology