Solar term lunar divination

In the Book of Changes, the algorithm of each month is not based on the first day to the thirtieth day, but on festivals. For example, in the first month, beginning of spring and beginning of spring, the festivals will be counted in silver moon, even if it is surprised in mid-February, it will be in Uzuki, even if it is Qingming in March. . . . . The boundary of a year is the beginning of spring.