The ancients didn’t have cable tv, so they spent a good amount of time watching the sky instead. Their knowledge of the positions of the constellations, of the sun and the moon cycles, and of the seasons was thorough and precise.
Not that thorough and precise. Remember not all of them figured out what was rotating around what. And if you don’t have the orbital mechanics down then eclipses can be surprising. But they were definitely paying attention and would have noticed eclipses.