Grand Campaign Medieval II Total War?

Question

How do you change the time, like in the first one it had early, middle, late; how can you do it this time? (Grand Campaign)

Answer 1

I believe the only time you can advance to a more...well...'advanced' age is if you use the campaign builder. Of course that allows you to chose time, location, season, etc.
As far as the Grand Campaign goes the object is precisely what it lists at the bottom left of the screen for campaign options. Short or long campaign.

You're supposed to keep your kingdom alive and thriving and advance into the 1500's. So...I don't think you can arbitrarily move forward in time on a whim.