Since many of the worlds of FF don't have noticeable day/night cycles (cutscenes/changes of area don't count), it's hard to pintpoint a single amount of time that has passed on a game. Perhaps the one game that can be measured in a form of time would be FFX. During the game there are many times when time is obviously progressing (the ship to Kilika, half-way across the Mihen-Highroad etc.). However beyond the last part of the game it's possible to cross from one area to another and have the day obviously change quite quickly ((SPOILER)think walking from the calm lands to Zanarkand and back, in our time it would take about three hours, yet an obvious day/night cycle has occured).