Modern vs Medieval, what time is it?

[MistakeNot]

i would say Eorzea is in the equivalent of the post industrial revolution. So around the mid to late 1800's in our own time. Magic has definitely played a factor in how tech (particularly the rise of Magitek as a way to combat it by people unable to use magic themselves) has deviated from our own. Which would make the Imperial expansionist period of Garlemald similar to Germany's in WW1.

Well, no. Eorzea has most certainly not had an industrial revolution yet - just about everything is still handmade rather than massproduced in a factory.
The level of technology available is more or less equivalent to our 18th century - but it is very unevenly spread, just like it was in our world. Rich nobles may have access to fairly advanced technology, but poor peasants won't have such access.