August 15th is the Feast of the Assumption of Mary into Heaven.
In Roman Catholic doctrine, the Assumption means that Mary, the mother of Jesus, was taken (assumed) bodily into heavenly glory when she died. In the Orthodox church, the koimesis, or dormition ("falling asleep"), of the Virgin began to be commemorated on August 15 in the 6th century. The observance gradually spread to the West, where it became known as the feast of the Assumption. By the 13th century, the belief was accepted by most Catholic theologians, and it was a popular subject with Renaissance and baroque painters. The Assumption was declared a dogma of the Roman Catholic faith by Pope Pius XII in 1950.
My soul proclaims the greatness of the Lord, my spirit rejoices in God my Saviour; he has looked with favour on his lowly servant.
From this day all generations will call me blessed;
the Almighty has done great things for me and holy is his name.
He has mercy on those who fear him,
from generation to generation.
He has shown strength with his arm
and has scattered the proud in their conceit,
Casting down the mighty from their thrones
and lifting up the lowly.
He has filled the hungry with good things
and sent the rich away empty.
He has come to the aid of his servant Israel,
to remember his promise of mercy,
The promise made to our ancestors,
to Abraham and his children for ever. (Luke 1:46-55)