Control for calculating solar terms

According to the annual date of beginning of spring, 24 solar terms can be calculated, and the annual date of beginning of spring is calculated as follows:

Every15th day after beginning of spring is a solar term.

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, as simple as that.