Most accurate pendulum clock on the planet.
Can a pendulum clock be good to one second in 158 million years? A piece of
cake...
A bit of background
Clocks have been my hobby since years. I have built a number of
electronic or electromechanical clocks myself, it is an excellent
psycho-hygienic activity. Obviously the more obscure, the better. Digital
clock with relay logic, one line word-clock, voltmeter clocks, wristwatch
with numitron display and discrete logic (no microcontroller),VFD bar dot
indicator and discrete transistor logic, nix...
Read more at dvaluch.web.cern.ch