By Age

Figures they would have a test for dogs too - Dogage! " No more multiplying by 7 years to learn your dog's age in people years. The DogAge Test measures your dog's biological age, based on your dog's health, breed, risk of disease, and behavior."

Catage is a very good site where you give in various information such as if your cat is an indoor cat, if you're a smoker and what food you feed your cat in order to calculate it's age. I'll do another test now since the last one I did was over a year ago and I'll post the results...