Why is the winter solstice the shortest day and the longest night?

Among the 24 solar terms, the winter solstice is the shortest day and the longest night in the northern hemisphere.

In winter solstice, although the sun is low and the days are short, the temperature in winter solstice is not the lowest in meteorology. In fact, because there is still "accumulated heat" on the surface, it is usually not very cold before the winter solstice, and the real cold is after the winter solstice. Because of the huge climate difference in China, this climatic winter is obviously late for most parts of China. The winter solstice marks the beginning of the cold season, and people begin to count to nine to calculate the cold weather (folk proverb: "The summer solstice is the third watch, and the winter solstice is the ninth watch").

Winter solstice is one of the eight festivals in a year. Since ancient times, our ancestors have a tradition of offering sacrifices to their ancestors during the winter solstice to express their filial piety and not forget their roots. Due to different local customs and habits, the forms of ancestor worship are also different. While offering sacrifices to ancestors, they also offer sacrifices to the gods of heaven and earth. The offerings mainly include three sacrifices, three teas and five wines.

In many parts of northern China, it is a custom to eat jiaozi every winter solstice. According to legend, Zhang Zhongjing, a medical sage, saw a frozen person when he retired in his later years, so he wrapped mutton, some cold-dispelling herbs and dough into the shape of ears, made a medicine called "Quhan Jiaoer Decoction" and gave it to the people. Later, on the solstice of winter, people imitated eating and formed a custom.