1 An interval of a few months will again bring round that most happy day on which, fifty years ago, Our Predecessor Pius IX., Pontiff of holy memory, surrounded by a noble crown of Cardinals and Bishops, pronounced and promulgated with the authority of the infallible magisterium as a truth revealed by God that the Most Blessed Virgin Mary in the first instant of her conception was free from all stain of original sin. All the world knows the feelings with which the faithful of all the nations of the earth received this proclamation and the manifestations of public satisfaction and joy which greeted it, for truly there has not been in the memory of man any more universal or more harmonious expression of sentiment shown towards the august Mother of God or the Vicar of Jesus Christ.
Source: Ad Diem Illum Laetissimum (Vatican.va)