Telling the age of Grey tree frogs and White's tree frogs?

[BerryNight]

I have 2 grey tree frogs and 1 white's tree frog. I wanted to know the age of all of them but I don't know how or if it's even possible. I know that grey's live about 5-6 years and I caught them, I want to know how long I have with them. My white's looks juvenile and probably is and I also know that they live up to 15-20 years, or so I've read. I absolutely need to know! It's killing me not to! Please, if you know how to figure out the age of these types of frogs, please help me out soon!!!