How old is my guinea pig?

Question
Hi, I have been wondering how old my guinea pig is? How can i tell how old he is. Oh and do u think that they should have a sepcific bedding? The kind of bedding that i have is like cotton like material.  

Answer
It's really hard to determine the age without knowing some backgroound. most people who buy guinea pigs will just say how long they have had them and add four or five weeks to that. The bedding you are using sounds good. Is it carefresh or soft-sorbent bedding or something like that? Those are really good beddings.