For hundreds of years, Catholics observed the feast of the Assumption of the Blessed Virgin Mary on August 15. This teaching of Mary’s being taken bodily to Heaven after her death was in 1950 proclaimed a dogma of the Church, that is, the Assumption of Mary is one of the essential beliefs of the Catholic faith.
August 15 is the day that Catholics have long celebrated what is called the Dormition (falling asleep) or Assumption of the Virgin Mary. The Feast of the Assumption celebrates both the happy departure of Mary from this life by her natural death, and her assumption bodily into heaven.
Along with the Feast of the Immaculate Conception on December 8, the Assumption is a principal feast of the Blessed Virgin and a Holy Day of Obligation.
Though it was almost universally believed for more than a thousand years, the Bible contains no mention of the assumption of Mary into heaven.
The first Church writer to speak of Mary’s being taken up into heaven by God is Saint Gregory of Tours in 594.
On May 1, 1946, Pope Pius XII, asked all bishops whether they thought this belief in the assumption of Mary into heaven should be defined as a proposition of faith, and whether they with their clergy and people desired the definition. Almost all the bishops of the world replied in the affirmative.
On November 1, 1950, the Feast of All Saints, Pope Pius XII declared as a dogma revealed by God that “Mary, the immaculate perpetually Virgin Mother of God, after the completion of her earthly life, was assumed body and soul into the glory of Heaven.” (9:38)