Every year right before Christmas, there is an important oriental festival day fall on the Winter Solstice (冬至) which pronounced as Dong Zhi and directly translated to "extreme of winter". The Winter Solstice in 2009 is 22 December.
In Northern Hemisphere where China is located, the Winter Solstice is the day with shortest daylight (about 10 hours) and longest night (about 14 hours), which is the critical day of "Ying", when the solar celestial longitude reaches 270 degree and the sun has the lowest position in the sky. After this day, the daytime will become longer and longer, as more and more "Yang" re-entering. In Chinese saying is "阴极之至，阳气始生，日南至，日短之至，日影长之至".
After this day, the weather in the Northern Hemisphere will become cooler and cooler, until 9 x 9 = 81 days later, which is the last day of winter when the Chinese farmers start cultivating their farms again.
The Winter Solstice is an important festival to Chinese, which has equal significance with the Chinese New Year.
Similar to Chinese New Year, the Winter Solstice Festival is also a time for the Chinese family to get together, and eat the balls of glutinous rice named as Tang Yuan (汤圆) symbolizing "reunion". The Korean also practises similar culture too.
Traditionally, all the family members will make the Tang Yuan together using glutinous rice powder. Nowadays, ready made Tang Yuan is also available in the supermarket/hypermarket, and modern family just buy instead of making themselves. The Tang Yuan is boiled in water (with some brown sugar or salt, and pandan leaves) before consume in bowl.
Beside celebrated by oriental people, the Winter Solstice is celebrated globally, and the festival day might differ a little bit from the Chinese. Some Western Winter Solstice Festival fall on the Christmas Eve, and celebrated together with the Christmas Festival.
In fact, the celebration of Winter Solstice in mankind has longer history than Christmas, and people like Isaac Newton believed that the date of Christmas was selected to correspond with the Winter Solstice.