How old is Chang really?

In the S1 episode where he fakes his death and then comes in it shows a poster on the wall with his birth year and death year: http://imgur.com/ejgV4

In S1 episode 24 at 4:28 he says he is 32.

In the season 3 finale he says he is 25: http://www.hulu.com/watch/361762#s-p2-sr-i1

So in early 2009 we have a 20 year old Chang, then he jumps to 32ish, and then back down to 25?

Not only is he a Spanish genius, but he must have a time machine. So how old is he really?