When and how did humans first realize that it was darker/lighter on other parts of earth at the same time?

Question

I get how time zones were established, and I get how people knew the earth was round thousands of years ago, so I assume that it was hypothesized that some areas of earth were darker/lighter than others at the same time. I feel like it was kind of unprovable though due to limitation. At what point did we actually confirm that it was indeed night time somewhere else when it was daytime on the opposite side of the world? And how was the found out?

In: Other

Answer 1

Carl Sagan did a visual example of how Eratosthenes created an experiment that figured out a few things about how big the Earth was, and it’s position revolving around the sun.