Winter Solstice, also known as "Dongzhi", is the day with the shortest daytime and longest nighttime in a year. After the winter solstice, the daytime will start to increase gradually. Therefore, people eat tangyuan, a traditional Chinese food that symbolizes "reunion and completeness", to welcome the "yang energy". By eating tangyuan, people pray for everything to be complete and for their families to be reunited.

Traditionally, the winter solstice tangyuan is also known as "Dongzhi Yuan". It is small and unfilled, with two colors: red and white. Because the winter solstice is the day when the length of day and night "intersects", the red and white tangyuan also symbolize "yin and yang". Red represents happiness, while white is used to ward off evil spirits. Eating red and white tangyuan together is a way to achieve "yin and yang balance".