Forty Days after the Resurrection of Jesus Christ, the Acts of the Apostles records Jesus’ ascension into heaven. The ascension is an important Christian feast attesting and celebrating the reality of the God-Man Jesus Christ’s returning to the Father, to return again in the future parousia. The Ascension is the final component of the paschal mystery, which consists also of Jesus’ Passion, Crucifixion, Death, Burial, Descent Among the Dead, and Resurrection.
The Solemnity of the Ascension commemorates Jesus’ return to heaven 40 days after his Resurrection. Thus Ascension Day falls 40 days after Easter, on the 6th Thursday of Easter. In some parts of the world, the feast is transferred to the Sunday after the traditional date.
Evidence from John Chrysostom, Egeria, Gregory of Nyssa, and Church historian Socrates, suggest that Ascension Day probably originated in the 4th century AD. However, Augustine says the festival is apostolic. Often the feast was celebrated with a procession, symbolizing Christ’s journey to the Mount of Olives. Until rather recently, the Paschal Candle (lighted at the Easter Vigil) was extinguished on Ascension Day. It is often celebrated as an octave, the proper preface and Ascension collect being used until the Saturday before Pentecost. In many Catholic dioceses, the Ascension is celebrated on the 7th Sunday of Easter, which is the Sunday following the traditional date. Likely, this is done to make it easier for the faithful to fulfill their obligation to attend Mass on this day, but it removes the connection with the biblical chronology. (Source: ChurchYear.Net)