If they knew the earth rotated, then they could assume that noon happened at different times at different locations. But did they have a way to prove this without being able to travel or communicate fast enough to observe the effects?
In: Mathematics
It was known to scholars & navigators thanks to Magellan’s circumnavigation expedition. Magellan died, but one of his fellow captains, Elcano, arrived in Cape Verde Islands on what he thought was July 9 1522 and was told it was actually July 10 1522. This got people thinking about the concept of local time, but it would be another 350 years until Sanford Fleming proposed the whole time zone idea.
Eratosthenes calculated the circumference of the Earth in around 240BC, so the requisite knowledge was available, and really implicitly required for his calculation. The idea of “time zones” wouldn’t really be useful until accurate timekeeping was invented. If you don’t know what time it is where you are, it hardly matters what the time somewhere else is.
Yes. Ever since we proved the Earth was round we’ve understood this. So for somewhere in excess of 2,000 years.
The better question is “did they know when they were sleeping, people on the opposite side of the world were awake in daylight”
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