Summer solstice (summer solstice) June 2 1 or the 22nd of each year is the summer solstice. On the day of summer solstice, the sun directly reaches the northernmost part of the year, almost directly to the Tropic of Cancer (23 26' 28 ÷ 44 north latitude), and the daytime in the northern hemisphere is the longest, and the farther north it is, the longer it is. It is the longest day in a year in the northern hemisphere, and it takes about fourteen hours from sunrise to sunset in the south of China. 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 Celsius.

Summer solstice was also called "Summer Festival" and "Summer solstice Festival" in ancient times. In the ancient summer solstice, people prayed for disaster and prosperity by offering sacrifices to God. "Zhou Li Chun Guan" contains: "With the arrival of summer, go to local things." Sacrificing to God in the summer solstice of the Zhou Dynasty means eliminating plague, famine and starvation. Historical Records records: "On the solstice of summer, people worship the land with music and dance." As an ancient festival, the summer solstice began in the Song Dynasty, and officials have a three-day holiday. In Liao Dynasty, this day was called "summer solstice", and women entered colorful fans to give each other a legacy (Liao history). In the Qing dynasty, it was also called "summer solstice is a day's transition, and the sun, the next day and the last day were called" three hours ",so people lived cautiously.

Calculation of summer solstice date [Y*D+C]-L

Interpretation of the formula: Y= two digits after the number of years, D=0.2422, L= leap year, 2 1 century C=2 1.37, and 20th century =22.20.

For example, the date of summer solstice in 2088 = [88× .0.2422+21.37]-[88/4] = 42-22 = 20, and the date of summer solstice is June 20th.

Exception: 1928 plus 1 day.