Double Ninth Festival

The Double Ninth Festival ( or Chong Yang Festival), observed on the ninth day of the ninth month in the Chinese calendar, is a traditional Chinese holiday, mentioned in wrting since before the Eastern Han period (before AD 25).
According to the 1 Ching, nine is a yang number; the ninth day of the ninth lunar month ( or double nine) has too much yang ( a traditional Chinese spiritual concept) and is thus a potentially dangerous date. Hence, the day is also called Double "Yang Festival". To protect against danger, it is customary to climb a high mountain, drink chrysanthemum liquor and wear the zhuyu plant, Cornus officinalis. ( Both chrysanthemum and zhuyu are considered to have cleansing qualities and are used on other occasions to air out houses and cure illnesses.)
On this holiday some Chinese also visit the graves of their ancestors to pay their respects.

https://en.wikipedia.org/wiki/Double_Ninth_Festival