In the Eastern Church this feast was known as analepsis, the taking up, and also as the episozomene, the salvation.
According to the Catholic Encyclopedia, in the Eastern Church this feast was known as analepsis, the taking up, and also as the episozomene, the salvation, denoting that by ascending into His glory Christ completed the work of our redemption. The terms used in the West, ascensio and, occasionally, ascensa, signify that Christ was raised up by His own powers. Tradition designates Mount Olivet near Bethany as the place where Christ left the earth. The feast falls on Thursday. It is one of the Ecumenical feasts ranking with the feasts of the Passion, of Easter and of Pentecost among the most solemn in the calendar, has a vigil and, since the fifteenth century, an octave which is set apart for a novena of preparation for Pentecost, in accordance with the directions of Leo XIII.
The observance of this feast is of great antiquity. Although no documentary evidence of it exists prior to the beginning of the fifth century, St. Augustine says that it is of Apostolic origin, and he speaks of it in a way that shows it was the universal observance of the Church long before his time. Frequent mention of it is made in the writings of St. John Chrysostom, St. Gregory of Nyssa, and in the Constitution of the Apostles. The Pilgrimage of Sylvia (Peregrinatio Etheriae) speaks of the vigil of this feast and of the feast itself, as they were kept in the church built over the grotto in Bethlehem in which Christ was born (Duchesne, Christian Worship, 491-515). It may be that prior to the fifth century the fact narrated in the Gospels was commemorated in conjunction with the feast of Easter or Pentecost. Some believe that the much-disputed forty-third decree of the Council of Elvira (c. 300) condemning the practice of observing a feast on the fortieth day after Easter and neglecting to keep Pentecost on the fiftieth day, implies that the proper usage of the time was to commemorate the Ascension along with Pentecost. Representations of the mystery are found in diptychs and frescoes dating as early as the fifth century.
Certain customs were connected with the liturgy of this feast, such as the blessing of beans and grapes after the Commemoration of the Dead in the Canon of the Mass, the blessing of first fruits, afterwards done on Rogation Days, the blessing of a candle, the wearing of mitres by deacon and subdeacon, the extinction of the paschal candle, and triumphal processions with torches and banners outside the churches to commemorate the entry of Christ into heaven. Rock records the English custom of carrying at the head of the procession the banner bearing the device of the lion and at the foot the banner of the dragon, to symbolize the triumph of Christ in His ascension over the evil one. In some churches the scene of the Ascension was vividly reproduced by elevating the figure of Christ above the altar through an opening in the roof of the church. In others, whilst the figure of Christ was made to ascend, that of the devil was made to descend.
In the liturgies generally the day is meant to celebrate the completion of the work of our salvation, the pledge of our glorification with Christ, and His entry into heaven with our human nature glorified.