When did it become relatively common knowledge in different regions/civilizations that if you go far enough east or west, time is different (i.e. It's night on one side of the world and daylight on the other)?
It'd also be interesting to hear about civilizations that did not spread wide from east to west (like the Incans). It would also be interesting to know when people became aware that different latitudes had different lengths of day depending on the time of year.
The FAQ's answers, and other postings I've found in AskHistorians, covers only Western culture: ancient Greece, ancient Rome, medieval England, and Columbus. So previous answers are starting points, not to discourage follow-on questions, information, and debate, all of which are welcome.
There are links in the FAQ section "Clocks / Time zones and time differences" at https://www.reddit.com/r/AskHistorians/wiki/language#wiki_clocks . (In the app, the # anchor doesn't work, so you have to look for that section header.) In particular, in "At what point did humans understand the existence of timezones - i.e. that the sun didn't rise and fall the same way everywhere?", /u/jschooltiger cited the proposal of Hipparchos, which covers Greece in antiquity. That discussion also has the reply of /u/restricteddata on the difference between "time zone" and the notion that local noon varies.