When is the baby full moon?

We have a custom here that the boy's full moon is shortened by one day and the girl's full moon is postponed by one day. If it's two children born on the ninth day of the first lunar month, if it's a boy, it's full moon on the eighth day of February, if it's a girl, it's full moon on the tenth day of February. There are good wishes in it, passed down from generation to generation! ! ! !