Thanks Joe for your short & sweet answer to @adrian.
I don’t know those dates off the top of my head - had to do a search. Lifted my heart to find the following (bolding is mine)
POPE PIUS IX PROCLAIMS THE DOGMA OF THE IMMACULATE CONCEPTION
On December 8, 1854, having spent all of his holy life – his boyhood, his priesthood, as bishop, cardinal and Pope – at the feet of the Mother of God, the most Blessed Virgin Mary, and having deeply considered also, in his exile at Gaeta, the earnest petitions of Catholics all over the world in its behalf, Pope Pius IX defined ex cathedra, in the glorious Basilica of Saint Peter’s before one hundred and seventy bishops and innumerable pilgrims come literally from the ends of the earth, the divine dogma of Our Lady’s Immaculate Conception. The voice of the Sovereign Pontiff broke and tears filled his eyes as he paused before uttering the infallible words:
“We declare, pronounce and define that the doctrine which holds that the Blessed Virgin Mary, at the first instant of her conception, by a singular privilege and grace of the Omnipotent God, in virtue of the merits of Jesus Christ, the Savior of mankind, was preserved immaculate from all stain of original sin, has been revealed by God, and therefore should firmly and constantly be believed by all the faithful…”