The clock reference, in other words the heart beat of this clock comes from the AC outlet. Here in North America, the outlets supply 120 Volts, in 60 cycles per second, called 60 Hertz. This 60 Hertz signal is taken by the clock and is divided by sixty to produce a pulse of 1 hertz, which is one pulse per second. The same circuit which does this division is also used to animate the ring of LED lights around the clock digits. The 1 Hertz pulse is then taken to the seconds counter, then to the tens of seconds counter, then to the minutes, and so on, till the tens of the hours.

Magnifique
C'est énorme !