Let's talk dog for a minute.

If you want to know how old your dog is forget that old 7 year formula. 

Your dog ages quickly the first couple of years of life.  A 2 year old dog is 21 in human years.  After two, however, aging slows down for your four legged buddy.  It's more live 4 human years for every dog year. 

Dog Whisperer Cesar Millan says the best way to estimate a dogs age is to use this formula;  Subtract 2 years from your dogs age, multiply that by 4 and add 21.