Keeping Time

My own Discworld "Vetinari Clock"
Inspired by a comment on a Reddit joke.

When I was in high school there was a wall clock in each classroom. The clocks were all controlled by a master controller in the office. After school the power was shut down and the clocks stopped. In the morning, the power is turned on, and the master controller pulses all the clocks rapidly until they caught up to the correct time. At any rate, that was the story I heard. Now that I think about it, they could have just stopped the clocks at 6PM and then resumed at 6AM and it would have accomplished the same thing.

It seems like an awfully involved system for keeping the clocks running on time. I suppose the one advantage it has is that if there is a power failure, you only have to update the time on the master clock. You don't have to go around to all the classrooms and set the time on each clock individually. It might have been an IBM system. It sounds like something they would do.