The Winter Solstice Festival or The Extreme of Winter (Chinese: 冬至) is one of the most important festivals celebrated by the Chinese and other East Asians during the dong zhi solar term on December 22 or 23* when sunshine is weakest and daylight shortest; i.e., on the first day of the dongzhi solar term.
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 'fu' (復, "Returning"). Traditionally, the Dongzhi Festival is also a time for the family to get together. One activity that occurs during these get togethers is the making and eating of "tang yuan"(湯圓) or balls of glutinous rice, which symbolize reunion.