Winter solstice is the first solar term.
The annual solar calendar is 65438+February 2 1 or 22, and the winter solstice is the time when the sun reaches 270 degrees of the yellow meridian. The winter solstice marks the official start of winter, which also means shorter days, longer nights and colder weather. The solstice in winter is the extreme point of direct sunlight spreading to the south. On the solstice of winter, the sun shines directly on the tropic of Capricorn, and the sun is most biased towards the northern hemisphere. The elevation angle of the sun is the smallest, which is the shortest day and the longest night in all parts of the northern hemisphere.
In addition, the winter solstice is also a traditional ancestor worship festival in China. The solstice in winter is one of the eight festivals in four seasons, and it is considered as a big holiday in winter. In ancient times, there was a saying that the winter solstice was as big as a year. In southern China, there are customs of offering sacrifices to ancestors and enjoying the winter solstice. In the northern region, there is a custom of eating jiaozi from winter to Sunday every year.
Winter solstice solar terms
Winter solstice is one of the "24 solar terms". "Twenty-four solar terms" and "December construction" are the basic contents of the calendar, which were concluded in ancient times (or ancient times). According to ancient records, Emperor Tiandi began to determine his age in the name of cadres and branches. "Twenty-four solar terms" is a special festival in the calendar, indicating the season, phenology, climate change and the establishment of "December construction". In ancient times, the "twenty-four solar terms" were determined by the direction of the top of the Beidou bucket handle, and the solar terms of the winter solstice were determined when bucket handle pointed to the "minute" position of due north.
The names of the twenty-four solar terms first appeared in the Western Han Dynasty document "Tian Zi Xun in Huainan". During the period of Emperor Wu of the Han Dynasty, the twenty-four solar terms were absorbed into the taichu calendar, as a supplement to the calendar guiding farming, and the solar terms were divided by the method of "leveling" (that is, the average time method). The "flush method" uses photogrammetry to determine that the day in the Yellow River basin is as short as the winter solstice, and divides the date between the winter solstice and the next winter solstice into twelve equal parts. It is called "Zhongqi", and then the dates between adjacent "Zhongqi" are divided equally, which is called "solar terms".