sun and sundials

High quality telescopes have been around since Copernicus. Use a scope with a cross hair and align it with a known star at night. This is infinitely more precise than a sundial.

it started with sundials. when they figured out how to make a mechanical clock, they just set the time based on the sundial. old mechanical clocks work the same way todays mechanical clocks do. The only thing that has changed is the face. Any time the clock would go slow they would fix the mechanics and refer back to the trusty sundial. How do you open a new pair of scissors i you dont already have a pair to get through that thick plastic? Use a knife.