Therefore, she can be 31, but yet in 2012 or 2013 or whatever, because she was dropped off only minutes after her leaving
Well okay, but the year is likely 2016 by now. After all, S6 was set in 2011. The Ponds' cameo in the Christmas special was "two years later" making it 2013. There was no indication when Asylum of the Daleks place, though logic suggest it has to be sometime within 2014. Since Pond Life part 5 is in August, Asylum could be as well, or perhaps September since that's the month when it aired. Dinosaurs on a Spaceship is ten months after Asylum, making it June or July 2015. Since The Power of Three goes from July of one year to July of the next, we can assume it's July 2015 to July 2016. So, Amy is 31 four years before she should be.