Winter Solstice, an important node of the 24 solar terms in China, is the shortest day and longest night north of the equator on Earth. The winter solstice is the peak of the sun‘s southerly journey, when the sun is at its lowest altitude in the northern hemisphere. On this day, the sun shines directly at the Tropic of Capricorn, and the sun‘s rays are most tilted towards the northern hemisphere. The winter solstice is the turning point for the sun to travel south. After this day, it will "turn back", the direct point of the sun begins to move north from the Tropic of Capricorn (23°26 ‘S), and the northern Hemisphere (China is located in the northern hemisphere) will increase day by day. Since the Earth is near the perihelion around the winter solstice, it moves slightly faster, which results in the time of the year when the sun is directly in the southern Hemisphere, which is about 8 days shorter than the time directly in the northern Hemisphere, so the winter in the northern Hemisphere is slightly shorter than the summer.

In many parts of north China, there is a custom of eating dumplings on the Winter solstice every year. People in northern China eat dumplings on this day because dumplings have the meaning of "dispelling cold". There is still a folk saying that "if you don‘t serve dumplings on the Winter solstice, you will freeze your ears."

In the traditional customs of Ningbo, sweet potato soup is one of the winter solstice food. "Fan" and "turn" homophone, in the understanding of Ningbo people, eating sweet potatoes during the winter solstice is to "turn" all the bad luck of the past year. Fruit soup, similar to gnocchi, but much smaller and with no filling. Tangguo is also called Yuanzi, taking its "reunion", "complete" meaning. Old Ningbo also has the saying that "eating soup is one year older". Ningbo people are used to adding wine when making sweet potato soup. In Ningbo dialect, wine is also called "pulp board", "pulp" and Ningbo dialect "rise" homonym, take its "wealth rising", "good luck rising".