The Winter Solstice Festival has its origins in the Chinese concept of yin and yang, which represents balance and harmony in life. It’s believed that the yin qualities of darkness and cold are at their most powerful on the shortest day of the year, but also at their turning point to give way to the light and warmth of yang. Along with the longer daylight everyday, Yang energy increases day by day until it reaches its climax on summer solstice.
Traditionally on this day the Northern Chinese would eat dumplings (jiaozi 饺子) or won tons (huntun 馄饨), and the Southern Chinese eat glutinous rice balls (tangyuan 汤圆). Though they use different ingredients, have different shapes and tastes, they all use a sort of dough to wrap the fillings.
Starting from the winter solstice day, the weather is getting colder. The ancient Chinese begins to count days by every 9 days as one length of time. After 9 times in total 81 days, it is believed the warm weather should come. During this period it is a tradition to take foods more warm and yang by nature, for example, lamb, beef, chicken, black sesame, red date, walnut, etc.