Double Ninth Festival (重九, also Chung Yeung Festival 重陽節 in Hong Kong) dated on the ninth day of the ninth month in Chinese calendar, is a traditional Chinese holidays, mentioned in writing since before the East Han period.

According to the I Ching, nine is a yang number, ninth day of the ninth lunar month or double nine, has too much yang and is thus a potentially dangerous date. Hence, the day is also called "Double Yang Festival" (重陽節). To protect against the danger, it is customary to climb a high mountain, drink chrysanthemum wine, and wear a plant named zhuyu (茱萸). Both chrysanthemum and zhuyu are considered to have cleansing qualities and are used to air out houses and cure illnesses.

Double Ninth may have started out as a day to drive away danger, but, like the Chinese New Year, over time it became a day of celebration. Today it is an occasion for hiking and chrysanthemum appreciation. Stores sell rice cakes (糕 a homonym for height 高) inserted with mini colorful flags to represent zhuyu. Most people drink chrysanthumum tea, a few old schools drink homemade chrysanthemum wine. School children learn poems about chrysanthemum, and many cities will host a chrysanthmum exhibit. Mountain climbing races are also popular, winners get to wear a wreath made of zhuyu.

This is an often quoted poem about this holiday:

《九月九日憶山東兄弟》 王維

獨在異鄉為異客，

每逢佳節倍思親，

遙知兄弟登高處，

遍插茱萸少一人。

Double Ninth, Missing My Shantong Brothers _ Wang Wei (Tang Dynasty)

Alone, a stranger in a strange land,

Every holiday the homesickness doubles.

Far away my brothers have sent word:

They have gathered on mountain tops,

They are going around inserting zhuyu branches,

They are missing one person.