The Winter Solstice (alias: Winter Festival, Long Solstice Festival, Asian Year, English name: Winter Solstice) is the 22nd solar term of the "Twenty-four Solar Terms", and the solar longitude reaches 270 degrees, which falls on December 21st, 22nd or 23rd of the Gregorian calendar every year. It is a traditional festival of the Chinese nation. The custom of celebrating the winter solstice originated from the Han Dynasty and flourished in the Tang and Song Dynasties.

The winter solstice is the extreme point where the direct sunlight travels southward. On the winter solstice, the sun shines directly on the Tropic of Capricorn, and the sun is the most inclined to the northern hemisphere, with the smallest sun elevation angle. It is the shortest day and the longest night in all parts of the northern hemisphere. The winter solstice is also the turning point of the sun's direct point of return to the north. After this day, it will take a "turning back", and the sun's direct point will begin to move northward from the Tropic of Capricorn (23 26' s), and the daytime in the northern hemisphere will increase day by day. The winter solstice marks the beginning of the cold season, so the people began to count nine to calculate the cold weather (folk proverb: "The summer solstice is three Geng, and the winter solstice counts nine for everyone).

There is a folk saying that "the winter solstice is as big as a year", but there are different customs in different places during the winter solstice. Most people in the north have the custom of eating dumplings, while most people in the south have the custom of eating tangyuan.