虚岁

xū suìxusui

1. one's age, according to the traditional Chinese method of reckoning (i.e. the number of Chinese calendar years in which one has lived) – In this system, a person's age at birth is one, and increases by one at the beginning of the first solar term 立春[Li4 chun1] each year, rather than on one's birthday.
2. contrasted with 實歲|实岁[shi2 sui4]

Study it in Yanamino