The Long Now Foundation has spent a lot of time thinking about this. They have designed and implemented clocks built to last 10,000 years. I doubt anyone else h

The Long Now Foundation has spent a lot of time thinking about this. They have designed and implemented clocks built to last 10,000 years. I doubt anyone else has spent as much time and effort solving this problem, so I’d suggest something similar: https://longnow.org/clock/ https://longnow.org/clock/