An algorithm for finding twenty-four solar terms. Non-lookup table method.

Solar term date speed algorithm: general birthday formula -[y× d+c]-l

Y= year, D=0.2422, L= leap year, and C depends on solar terms and year.

In this century, the C value of beginning of spring is 4.475, and the beginning of spring date of 20 17 is as follows:

[20 17×0.2422+4.475]-[20 17/4- 15]=492-489=3

So the beginning of spring date of 20 17 is February 3rd, but the value of c in the formula is different every century. So we still need to check the c value. You can find the source program of the longevity calendar to study the specific C value.