Ascension Day is the fortieth day of Easter and commemorates Jesus ascending to heaven after his resurrection on the first Easter Day. The feast therefore always falls on Thursday.
According to the accounts in the Gospel of Luke and the Acts of the Apostles, Jesus appeared to many of his disciples during the days following his resurrection. On the fortieth day, he came again to the Apostles and led them out to the Mount of Olives where he instructed them to wait in Jerusalem for the promise of the Holy Spirit. Then, as they were watching, he ascended and was lost to sight. As they continued to look skyward, two angels appeared and declared to them that, just as he ascended, Jesus would return in glory.
Tradition designates Mount Olivet near Bethany as the place where Jesus left the earth.
Christians have celebrated the Ascension since very ancient times. The earliest surviving paintings and altar pieces date from the fifth century, but St Augustine of Hippo and his contemporaries (writing in the 350s) say the Apostles themselves celebrated the Ascension. Perhaps they celebrated with a single continuous feast between Easter and Pentecost.
In the Eastern Churches this feast was known as analepsis, ‘the taking up’, and as the episozomene, ‘the salvation’ — suggesting that by ascending into His glory, Christ completes the work of our redemption. The Latin terms used in the West, ascensio (and, occasionally, ascensa) signify that Jesus was raised up by his own powers.
The Ascension (1958) Salvador Dali.