The Double Ninth Festival, the ninth day of the ninth lunar month, the twenty-ninth phase, called "Double ninth", the folk custom of climbing on that day, so the Double Ninth Festival is also called "climbing Festival". There are double ninth Festival, dogwood, chrysanthemum festival and so on. Since the ninth day of September "99" homophonic is "long", there is a long-term meaning, so often in this day ancestor worship and the implementation of respect for the elderly activities.

The Double Ninth Festival, together with the three festivals of the Qing Dynasty and Yu, are also the four major festivals of ancestor worship in traditional Chinese festivals. On December 28, 2012, the law clarified that the ninth day of the ninth lunar month is the Old People's Day every year.