Question

How did the humans set the first clock ;it is known that the first clock was a sundial but how did they get the angle of the shadow?

Answer 1

They kept observing it, and day by day, they figured out that at a specific angle of the shadow, the sun would be rising, etc..., and at a specific angle, the sun would be setting. They would stand at a specific place in front of the sundial, and see the shadow.