In terms of all the FF games I've played, X has been the shortest (sans XIII).

For me, all the time up to the entrance to Luca would have been say five days at most. After that, it get's slightly more ambiguous. Up until the end of Macalania, you can sort of predict the days as they go on, however after being washed up in the desert it becomes alot harder.

The events at Bevelle might have taken a few days; hosting a wedding takes some prep work, even if it is rather shotgun style. The Calms Lands I see also taking 2-3 days, while Mt Gagazet takes just one day.

From Baaj Temple ---> Sin, I would say it would be say at least 2 months. Maybe even more.