The traditional age in China is nominal age, which is calculated according to the lunar calendar. At birth, it is 1 year-old, and it increases by 1 year-old every Spring Festival. It is seven years old this year.
According to the Gregorian calendar, one year old is 0 years old, and every birthday is increased by 1 year old. Now he is 5 years old, and he will be 6 years old this year in the solar calendar 1 18.