Carey's approach to world-building has always been "pick the cool time period of an area, regardless of whether it makes any sense (or is even possible) with the adjoining areas". Which is cracktastic in a way that appeals to my id very often.

Off the top of my head, the Phedre books featured a High Medieval France, Renaissance Venice, Early Medieval or Late Classical Germany, Dynastic Egypt, Iron Age Ireland, and a seriously race-faily Generic Middle East with Elements from Many Time Periods.