I don't think it's really possible to do it the way you want it in civ. That would require unique historical periods for different "civs" and unique technology trees for different parts of the world. We use the western standard eras because they are familiar to us but actually these really only applies to western europe and it's colonial hiers in the new world. The rest of the world have not only different dates for eras but different eras aswell. The middle ages is for example when China pretty much invented everything the europeans would "invent" in the renaissance, and the Arabs absorbed every knowledge they could from the people they conquered and added more to the mix. It certainly wasn't a middle age for them.