How a quartz watch works

How do quartz watches keep time? Steve Mould gives a great demonstration explaining how they work. Quartz is piezoelectric, which means when it is deformed it generates an electrical signal. A quartz watch has a tiny quartz tuning fork that's been calibrated to vibrate at 2¹⁵ cycles per second. This signal is fed through a series of 14 flip-flop circuits, each of which divides the frequency of the signal by 2. By the time the signal goes through the 14th flip-flop, the frequency is one cycle per second.