[epcoa]

"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.

[poooogles]

Why not both?

https://en.wikipedia.org/wiki/Spring_Drive

Advertised at +-15 seconds a month, but in reality it's much better than that.