Assumption (Dormition) is one of the twelve great church holidays; it’s celebrated on August 28.
The history of the Orthodox Church feast of the Assumption of the Virgin Mary is follows. After the death and resurrection of Jesus Christ Virgin Mary had spent 10 years in Jerusalem, preaching, like the apostles, the Christian faith, telling people about the life of Christ.
Before the great Orthodox holiday of the Assumption the Lord gathered all his students in Jerusalem - already apostles. And they came together only because of the real miracle: each of the apostles, who preached the Bible, was taken by the air swirl in the clouds and brought straight to the house of St. John the Divine, where Mother of God lived.
When apostles understood the essence of their miraculous arrival into the house of the Virgin, they were upset and crying. But Mother of God comforted them, promising to pray for them and be their intercessor after their death, their Assumption.
The moment of the Assumption of Virgin Mary is wonderful: when she was lying helplessly on the bed, her face suddenly lit up with an unprecedented light and radiant with joy –the roof of the house of the apostle John Divine opened wide due to the impossible bright rays of heavenly light, and right before the bed of Mother of God there appeared her Son - Jesus Christ himself. He was surrounded by the great number of Archangels, Angels and other members of God's army, and he was surrounded on all sides by the souls of the prophets, saints, patriarchs and righteous men.
This day is considered a holiday, because the very word "Assumption" indicates that the death of the Mother of God was extraordinary. This was like a brief sleep, followed by the birth into eternal life.