1. The winter solstice, also known as the short solstice, winter festival and sub-year-old, has both natural and humanistic connotations. It is not only an important solar term among the 24 solar terms, but also a traditional folk festival in China. The winter solstice is one of the four seasons and eight festivals, which is regarded as a big holiday in winter. In ancient times, there was a saying that the winter solstice was as big as a year, so the ancients called it "sub-year" or "off-year". The custom of winter solstice is different in content or detail because of different regions. In some areas along the southern coast of China, there is a custom of offering sacrifices to ancestors on the winter solstice; In the northern part of China, it is a custom to eat jiaozi every winter solstice.

2. The winter solstice is the 22nd solar term of the "Twenty-four Solar Terms", with the solar meridian reaching 27, and it is celebrated on December 21-23 of the Gregorian calendar every year. The winter solstice marks that the height of the sun in the northern hemisphere is the smallest and the daytime is the shortest, but the temperature on the winter solstice is not the lowest. On the winter solstice, the sun shines directly on the ground and reaches the southernmost point of the year. The sun shines almost directly on the tropic of Capricorn, and the sun is most inclined to the northern hemisphere.

3. The winter solstice is the day with the shortest day and the longest night in all parts of the northern hemisphere, and the days get shorter as you go north. After the winter solstice, the direct point of the sun gradually moved northward, and the days in the northern hemisphere began to lengthen gradually; Therefore, the ancients believed that the winter solstice was the weakest day of the year, and then the yang gradually picked up. From the winter solstice, the people began to count nine to calculate the cold weather. As the folk proverb goes, "The summer solstice is three Geng, and the winter solstice is nine."