"It's also the only timekeeping device that will still work after three days away from an electric plug"
https://en.wikipedia.org/wiki/Quartz_clock
Lasting years on a battery is easy.
https://en.wikipedia.org/wiki/Quartz_clock
Lasting years on a battery is easy.
https://en.wikipedia.org/wiki/Spring_Drive
Advertised at +-15 seconds a month, but in reality it's much better than that.