The Feast of the Immaculate Conception of the Blessed Virgin Mary
is today. There is information on it here.

It is a plain truth that the Blessed Virgin would not have been blessed, though she had been the Mother of God, if she had not done His will, but it is an extreme thing to say, for it is supposing a thing impossible, it is supposing that she could be so highly favoured and yet not be inhabited and possessed by God's grace, whereas the Angel, when he came, expressly hailed her as full of grace. "Ave, gratia plena." The two blessednesses cannot be divided. (Still it is remarkable that she herself had an opportunity of contrasting and dividing them, and that she preferred to keep God's commandments to being His Mother, if she could not have both.) She who was chosen to be the Mother of God was also chosen to be gratia plena, full of grace. This you see is an explanation of those high doctrines which are received among Catholics concerning the purity and sinlessness of the Blessed Virgin. St. Augustine will not listen to the notion that she ever committed sin, and the Holy Council of Trent declares that by special privilege she through all her life avoided all, even venial sin. And at this time you know it is the received belief of Catholics that she was not conceived in original sin, and that her conception was immaculate.

Whence come these doctrines? They come from the great principle contained in our Lord's words on which I am commenting. He says, "More blessed is it to do God's will than to be God's Mother." Do not say that Catholics do not feel this deeply—so deeply do they feel it that they are ever enlarging on her virginity, purity, immaculateness, faith, humility and obedience. Never say then that Catholics forget this passage of Scripture. Whenever they keep the Feast of the Immaculate Conception, the Purity, or the like, recollect it is because they make so much of the blessedness of sanctity. The woman in the crowd cried out, "Blessed is the womb and the breasts of Mary." She spoke in faith; she did not mean to exclude her higher blessedness, but her words only went a certain way. Therefore our Lord completed them. And therefore His Church after Him, dwelling on the great and sacred mystery of His Incarnation, has ever felt that she, who so immediately ministered to it, must have been most holy. And therefore for the honour of the Son she has ever extolled the glory of the Mother. As we give Him of our best, ascribe to Him what is best, as on earth we make our churches costly and beautiful; as when He was taken down from the cross, His pious servants wrapped Him in fine linen, and laid Him in a tomb in which never man was laid; as His dwelling place in heaven is pure and stainless—so much more ought to be—so much more was—that tabernacle from which He took flesh, in which He lay, holy and immaculate and divine. As a body was prepared for Him, so was the place of that body prepared also. Before the Blessed Mary could be Mother of God, and in order to her being Mother, she was set apart, sanctified, filled with grace, and made meet for the presence of the Eternal.

Venerable John Henry Newman, C.O., Faith and Prejudice and Other Unpublished Sermons