The stem before the month is called the moon column, which is not calculated according to the beginning and end of the month, but according to the change of odd solar terms in the 24 solar terms. For example, when it begins to rain in spring, the moon column will not change until it is awakened.
The 16th and 17th of the first month of that year should be the change of beginning of spring and scenery, and the moon column will naturally change.