This system is extremely practical. A child does not have to learn a new answer to the question, "How old are you?" in each new year. Old people often lose track of their age, because they are rarely asked about their current age. Every one just have to remember that he or she was born in the "Year of Dog" or whatever.
Since this is the Year of Dog, any one who was born in the Year of Dog is now either 0 or 12, 24, 36, 48, 60, 72, 84 or 96 years old.
Rat (the start of the Chinese Zodiac)
Tiger (or cat)