I'm not entirely certain, but going by the scenarios & some leader 'Pedia entries, the bulk of post-Age of Ice recorded FFH history takes place over the course of about 60 years. Capria is a young woman when the Bannor emerge from Hell shortly after the end of the AoI, and elderly by the time Hyborem is banished back to the underworld near the very end of the timeline. Each turn in the game is likely far less than one year in length- in some scenarios like the Momus, they can't possibly be more than a week.
Obviously none of the above applies to personal games, only for the general framework canon.
Obviously none of the above applies to personal games, only for the general framework canon.