Hate to burst your bubble but Kerwon and Purvama cannot be Ordalia and Valendia.

Mostly cause both regions already exist in XII's time and you visit one of them. Ordalia is to the west of where XII takes place and is occupied by the military state of Rozarria. Valendia is the region where Archades is located (and Lea Monde ) while Kerwon is Rabanastre and most of where XII takes place. Purvama is sealed at this time but but regions like Bhujerba suggest that floating islands are rather common in this universe.

Besides, if the Occuria could manipulate time and space, then how could destroying their Nethicite "break men from the shackles of oppression" by their rule?