Why is the summer solstice this year June 2 1?

Because a solar year (tropical year) is 365.2422 days, if there is no leap year, the appearance of the summer solstice will be delayed by 0.2422 days (about 5 hours and 48 minutes) year by year, so it is necessary to adjust the leap year. In this way, the same solar term differs by at most one day. (Actually, it's less than 24 hours, but the date may be one day. ) June 2 1. Although the summer solstice has the longest day and the highest sun angle, it is not the hottest time of the year. Because, close to the surface of the heat, at this time still continue to save, did not reach the maximum time. As the saying goes, "Hot days are in dog days", and the real hot weather is calculated by summer solstice and beginning of autumn. From mid-July to mid-August, the temperature is the highest in all parts of China, and the highest temperature in some areas can reach about 40 degrees. Solstice is the earliest festival in China. Before the Qing dynasty, there was a national festival on the solstice of summer. I went home to reunite with my relatives and have a drink. The Book of Rites also records the obvious phenomenon of solar terms in nature from summer to solar day: "From summer to solar day, antlers are untied, cicadas begin to sing, Pinellia ternata is born, and hibiscus is glorious." It shows that the antlers can be cut at this time, cicadas begin to sing, and Pinellia ternata and hibiscus gradually bloom. According to the theory of traditional Chinese medicine, summer is the season with the highest yang. Health care should conform to the characteristics of abundant yang in summer, pay attention to protecting yang, and focus on a "long" word.