According to the I Ching, nine is a yang number; the ninth day of the ninth month in the Chinese calendar (or double nine) has extra yang (a traditional Chinese spiritual concept) and is thus an auspicious date.[4] Hence, the day is also called "Double Yang Festival" (重陽節).[5] It is customary to climb a mountain,[6][7] drink chrysanthemumliquor,[6][7] and wear the zhuyu (茱萸) 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.[7] In Hong Kong and Macau, whole extended families head to ancestral graves to clean them, repaint inscriptions and lay out food offerings such as roast suckling pig and fruit, which are then eaten (after the spirits have consumed the spiritual element of the food). Chongyang cake is also popular[5] and incense sticks are burned during the holiday.[8]
^National Folk Museum of Korea (2015). Encyclopedia of Korean Seasonal Customs: Encyclopedia of Korean Folklore and Traditional Culture. Gil-Job-Ie Media. p. 232.