The Mid-Autumn Festival celebrates the full moon as a symbol of family reunion. Eating mooncakes (月饼 yuèbǐng) is the central tradition. It usually falls in September or October on the Western calendar.
history
The legend of Chang'e (嫦娥 Cháng'é) is deeply tied to this festival. She drank an elixir of immortality and flew to the moon, where she lives forever with the Jade Rabbit (玉兔 Yùtù).
culture
"但愿人长久,千里共婵娟" — famous line by Song dynasty poet Su Shi, recited every Mid-Autumn Festival. Means "May we live long and share the moonlight across a thousand miles."