The Winter Solstice occurs when the sun's position in the sky is at its greatest distance away from the Earth, resulting in what is the shortest day (and conversely, the longest night) of the year. Depending on changes in the calendar, the winter solstice occurs some time between December 20 and December 23 each year in the northern hemisphere. This year (2008), the solstice falls on December 21.

The seasonal significance of the winter solstice is that it indicates the reversal of the gradually lengthening nights and shortening days. Once winter solstice is past, the days become longer and longer. Because of this particular significance, most cultures have associated this day with rebirth, in the form of holidays, festivals, gatherings, rituals or other celebrations.

The origin of the winter solstice festival goes way back to ancient history. The ancient Egyptians, Babylonians and Persians all held festivals of renewal during this period, as did the Romans and other European cultures: the Roman Saturnalia, the Norse and Germanic Yule, and the Celtic festivals.
 
At the root of these celebrations and rituals is the battle between Light and Darkness. The battle reaches a turning point on the Winter Solstice as the forces of Darkness are halted and the tide turns in favor of the forces of Light, whose return to the earth promises to drive gloom away and to raise the spirits of people.

As in other cultures around the world, the Chinese also celebrate the festival. In fact, this is one of the most important festivals celebrated by Chinese around the world and other East Asian countries, and it is also the last major festival before the Chinese New Year. 

The Winter Solstice is called “Dong Zhi” in Chinese, which literally means "The Extreme of Winter." It is one of the 24 solar terms in the traditional Eastern lunar calendar, a system that matches a particular astronomical event or signifies some natural phenomenon.

Somewhat different from the idea of battles between Light and Darkness as envisioned in Western countries, to the Chinese the origins of this festival can be traced back to the philosophy of Yin and Yang, or balance and harmony in the cosmos. According to ancient Chinese thought, Yang stands for muscular or positive energy. After the festival is celebrated and past the days will offer longer daylight hours and therefore there will be an increase in positive energy Yang flowing in, so this day when the trend changes should be celebrated.

The Chinese first celebrated the winter solstice as early as 2,500 years ago, around the Zhou Dynasty (1045 BC to 256 BC) since that was when the Chinese had determined the occurrence of winter solstice by observing movements of the sun with sundials.
 
It was not until during the Han Dynasty (206 BC-220 AD), however, that “Dong Zhi” became an official festival and later thrived in the Tang and Song dynasties (618-1279). The Han people regarded “Dong Zhi” as a "Winter Festival." On this day both officials and common people would take a day off. Relatives and friends brought delicious food to each other and offered sacrifices to their deceased parents or other relatives.
 
The celebration of “Dong Zhi” reached its peak during Song Dynasty. Emperors would go to a temple to worship the god of heaven on this day, who would even announce amnesty to criminals during the festival to extend the idea of peace and harmony around the country.
 
There was a saying during the Qing Dynasty (1644-1911) that "Winter Solstice is as important as the New Year," which shows the great importance that was attached to this day.

Traditionally, like the Chinese New Year and Mid-Autumn Festival, Dong Zhi Festival is also a time for the family to get together to hold family reunions. It is on this day that people who are working far away from home come home to visit for a while.

Old traditions also require people with the same surname or from the same clan to gather at their ancestral temples to worship on this day. There is always a grand reunion dinner following the sacrificial ceremony.
 
Though in modern-day Chinese society people no longer follow some of the old Dong Zhi traditions, it is still very common for people to practice one of the most important rituals during the festival, which is eating a festive food called “Tangyuan.” “Tangyuan” is a kind small dumpling ball made of glutinous rice flour. The flour balls may be plain or stuffed with peanut powder or sesame paste. They are usually cooked in a sweet soup or savory broth with both the balls and the soup served in one bowl. Each family member receives at least one large “Tangyuan” in addition to several small red and white ones.

This festive food is eaten for several symbolic reasons. The word 'tang' means 'soup' and the word 'yuan' means 'round' or 'ball,' and when the two words are combined, the phrase is similar in sound with the term for “reuniting” (tuan yuan) in Mandarin Chinese.

Aside from its symbolic meaning, the festive food is also a reminder that we are now a year older and should behave better in the coming year. Even today, many Chinese around the world, especially the elderly, still insist that one is "a year older" right after the Dong Zhi celebration instead of waiting for the Chinese New Year.

To Taiwanese people, the festival in winter also plays a very important role. It is also a tradition for Taiwanese to eat “Tangyuan” during this day. They also use the festive food as an offering dish to worship the ancestors.

In an interesting twist, in accordance with ancient Taiwanese history, many people take some of the “Tangyuan” that have been used as offerings and stick them on the back of the door or on windows and tables and chairs. These “empowered” “Tangyuan” supposedly serve as protective talismans to keep evil spirits from coming close to children.

In addition to following some of the customs practiced in China, the people of Taiwan have their own unique custom of offering nine-layer cakes as a ceremonial sacrifice to worship their ancestors. These cakes are made using glutinous rice flour in the shape of a chicken, duck, tortoise, pig, cow or sheep, and then steamed in different layers of a pot. These animals all signify auspiciousness in Chinese tradition.

Another interesting custom in Taiwan is that many people take invigorating tonic foods during this particular winter festival. To the Taiwanese, winter is a time when most physical activities should be limited and you should eat well to nourish your body. This practice follows the habits shown by many animals which follow the law of nature and hibernate throughout winter months to rejuvenate and to preserve life. In order to fight cold temperatures, it is necessary to eat more fatty and meaty foods during winter when your body can better absorb the rich and nutritional foods at this time due to a slower metabolic rate.

Since “Dong Zhi,” is the “Extreme of Winter,” Taiwanese regard it as the best time of the year to take tonic foods. Some of the most widely-popular winter tonic foods enjoyed by Taiwanese to fight cold and strengthen the body's resistance are mutton hot pot and ginger duck hot pot. Other foods like chicken, pork and abalone are also common materials used in making tonic foods with nurturing herbs such as ginseng, deer horn and the fungus cordyceps.