Novena to the Holy Ghost Friday after Ascension Thursday -- Saturday, the Vigil of Pentecost This is the prototype of all novenas. It commemorates the nine days between the Ascension of Our Lord and the descent of the Holy Spirit on the first Pentecost Sunday. During this time Our Lady and the twelve Apostles prayed in the upper room for the coming of the Paraclete. https://www.ewtn.com/catholicism/devotions/novena-to-the-holy-ghost-826