How is the summer solstice calculated every year?

The summer solstice is the tenth of the 24 solar terms, which falls on June 2 1 or 22; It means that the heat is coming, with the longest day and the shortest night.

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: summer solstice date 2010 = [10× 0.2422+2 1 .37]-[88/4] = 21,summer solstice date 21.

Exception: 1928 plus 1 day.