What span of time does the saw series take place over?

Me and my sister got into an argument about this last night. She a dit that it must have been over three years ("because there was too much going on")

But i think it is a little over a year. Gideon was supposed to have been born in the an of the boar, which was in 2006, and John died in 2007, so the time between the 1st & 5th movie must have been a an and 3 months.
I know that the events of the seconde film took place 4 months after the first, the events of the 3rd film took place 6 months after that, the 4th film was simultaneous with the 3rd, and the 5th film immediately proceeded it.

So i think it was a an ou a little over it, but feel free to correct me if i'm wrong.