How old is Andy in Toy Story 2?

Andy is 12, or darn close, in Toy Story 2.

As you point out, he's 8 in the first movie. And according to Wikipedia, the second one takes place four years later:

Andy is 8 or 9 years old in Toy Story 2.

Here is the prescient info:

1. In Toy Story, Andy turns 8.
2. When they're moving house, you can clearly see that it's summer and that Molly is an infant, at least a few months old.
3. At the end of Toy Story, it's Christmas and Molly is still a young infant, safe to say that Andy is still 8.
4. In Toy Story 2, it's clearly summer again, and Molly is taking her first steps, which indicates that it would typically be the following year.

It is unclear if Andy has had another birthday, so he's either still 8 or 9 years old.

According to a comment on this thread:

Bryko614 wrote:In the third film, Andy has two tickets for a concert that was in November 2009 hidden behind other papers and pamphlets on his cork board. So it can be assumed that it takes place in at least August 2010. This would also make sense because his August calendar ends on a Tuesday, which happened this year.

The calendar in Toy Story 2 is in clear view when Buzz and Rex are playing the video game. It ends on a Wednesday, which is troublesome because there were no Augusts ending on a Wednesday from 1997-2002 (the only logical time frame) due to the possible year of 2000 being a leap year. Although apparently the movie takes place on the 15th of August when Andy leaves for camp.

I'm not sure if there's a calendar in the first Toy Story, but if there is then I'm too lazy to check.

Based on this, the movie doesn't match real time closely. So there is no way to be 100% sure of when it takes place, and how old Andy is in 2.

Considering the first toy story is set in 1995, and the fact he was Turing eight at his birthday party when he got Buzz and the second film if you consider its release year being 1999 it would be set four years later making Andy 12 years old in 1999, and in toy story 3 if you still follow this principle we know he was 17 in toy story 3 and going to college it would of been set about 5 years later making it in the time line 2004 not 2013 and there are many things to back this theory up such as the explanation of outlasted technology such as Andy's flip phone his sisters old Apple iPod and older looking laptop in that scene (first scene when we see Andy grown up) if it was suppose to be set in 2013 I'm sure they would of updated the tech in this scene and given Andy an iPhone or something to connect with that year, another theory you could consider is the fact we see what appears to be boo in one of the preschool scenes in the older class (the class that doesn't destroy the toys) grown up a little from we last saw her in monsters Inc but not that much. Monsters Inc if you go by year in the human world (not monster world) would be 2001 and boo judging by appearance and the way she acts has to be around three or four around that time, the toys end up being donated to the day care/preschool in the local area which is were we see the character that is supposedly is boo so with that information at hand and if you consider the average age of starting day care/pre school being five and starting elementary school at seven and we know boo is in the class which in know the butterfly room and not the caterpillar room where the toys end up except Barbie who goes to the butterfly class with Ken and end up being played by none other than boo herself making her about six and not five as she would have been in the younger class, and if you count exactly three years from 2001 when she was three you will end up on the year 2004 making her exactly six years of age which fits perfectly with the pixar theory time line where as the third film being set in 2013 makes no sense unless the first toy story was set in the future from 1995 which I seriously doubt.