[Lin]

Any time Saturn is within the aspect (applying, up to 7 degrees, separating about 3 degrees) it is active.(I'm talking about the square or other major aspects). If Saturn (or any heavy planets) will be returning to the exact aspect in it's retrograde or direct motion, it is considered square the entire time.
The difference between, let's say, the first pass and the last pass would be the OTHER planets aspecting both Saturn and the planet Saturn is squaring (in this case Venus) during each pass.
So if on the first pass Mars, let's say, is also negatively aspecting the Venus and on the last pass Mars is positively aspecing the Venus, etc, it will modifiy the square.
Also, you would want to see the transits in the chart of the other person...and how the transits change between the first and last passes in the composite chart.
LIN