Ascension Day is one of the main ChristianHoly Days. Itcelebrates the human body of Jesus (God the Son) going up to heaven to join God the Father 40 days after the Resurrection.
The story is told in the bible in three places: Luke 24:50-53, Mark 16:19 and Acts of the Apostles 1:9-11.
Some information about Ascension British traditions.