Ascension Day (also known as Ascension Thursday or Feast of the Ascension) refers to Jesus bodily ascending to heaven. According to the New Testament, the Ascension of Jesus occurring 40 days after the Easter on a Thursday (and ten days before Pentecost) but some religious celebrate it on Sunday in the sixth week following Easter Sunday. The Feast of the Ascension is one of the great solemnities in the Christian liturgical calendar.
The Acts of the Apostles says that after the resurrection Jesus stayed with his apostles for 40 days. Afterwards, they came to the Mount of Olives from where Jesus ascended to heaven to be with God. Following days prepare faithful for Pentecost.