The Winter Solstice (Dong Zhi, 冬至in Chinese) falls on sometime around Dec. 21-23, when the sun moves to the celestial longitude of 270 degrees. As early as 2500 years ago, Chinese people used earth sundial to measure the movement of the sun and determined the day of Winter Solstice ― the earliest decided term of the 24 traditional Chinese solar terms (a supplementary system in the Chinese calendar to guide farm work). On the day, the northern hemisphere gets the least sunshine ― 50% fewer than that on the southern hemisphere ― and the shortest daytime in a year.

The Chinese people have the custom of "Count Nine" (Shu Jiu, 数九in Chinese), a traditional way to indicate the weather changes during the period of about 80 days from winter solstice to spring equinox in the next year. The days of the period are divided into 9 groups of 9 days.

Winter solstice is also an important traditional festival in China, and customs vary in different areas of China. On the day, people eat dumplings in most parts of northern China, while people in Chengdu have the custom of drinking mutton soup since they believe it can help drive away coldness in the body.