The origins of this festival can be traced back to the Yin and Yang philosophy of balance and harmony in the cosmos. After this celebration, there will be days with longer daylight hours and therefore an increase in positive energy flowing in. The philosophical significance of this is symbolized by the I Ching hexagram fù (復, "Returning").
Traditionally, the Dongzhi Festival is also a time for the family to get together. One activity that occurs during these get togethers (especially in the southern parts of China and in Chinese communities overseas) is the making and eating of Tangyuan (湯圓, Cantonese jyutping: tong1 jyun2; Mandarin Pinyin: Tāng Yuán) or balls of glutinuous rice, which symbolize reunion. Tangyuan are made of glutinuous rice flour and sometimes brightly coloured. Each family member receives at least one large Tang Yuan in addition to several small ones. The flour balls may be plain or stuffed. They are cooked in a sweet soup or savoury broth with both the ball and the soup/broth served in one bowl.
In northern China, people typically eat dumplings on Dongzhi. It is said to have originated from Zhang Zhongjing in the Han Dynasty. On one cold winter day, he saw the poor suffering from chilblains on their ears. Feeling sympathetic, he ordered his apprentices to make dumplings with lamb and other ingredients, and distribute them among the poor to keep them warm, to keep their ears from getting chilblains. Since the dumplings were shaped like ears, Zhang named the dish "qǜ hán jiāo ěr tāng" or dumpling soup that expels the cold. From that time on, it has been a tradition to eat dumplings on the day of Dongzhi.