A dog was once the King of Norway for 3 years during the 11th centurey AD. The Norwegian King, angry his subjects once deposed him put Saur on the throne, demanding that he be treated regally.
To figure out your "true dog's age" in human terms, count the first full year as 15 years, the second full year as 10 yeas and all the following years as 3 years. In other words, a 5 year old dog would be: 15+10+3+3+3=34 years old.