Yeah, post-classical would have been the more accurate term, thought I'm not sure it would've had the same comprehensibility.
The "Classical" world is as limited as "the middle ages" (perhaps even moreso); it mostly deals with the Mediterranean civilisations - and Iran is a long way from there.
According to my AP World textbook, at least, classical refers to a lot of geographically diverse civilizations, from the Byzantines to the Song Chinese to the Aztecs
What's wrong with 14th century then?
Christianism. The man probably thought he lived around the year 800.