It began May 15. (Pentecost is May 24)
The Church's Most Powerful Novenas is a book of novenas connected with particular shrines. Michael Dubruiel wrote in the introduction to this book he compiled:
When Jesus ascended into heaven, he told his Apostles to stay where they were and to "wait for the gift" that the Father had promised: the Holy Spirit. The Apostles did as the Lord commanded them. "They all joined together constantly in prayer, along with the women and Mary the mother of Jesus, and with his brothers" (Acts 1:14). Nine days passed; then, they received the gift of the Holy spirit, as had been promised. May we stay together with the church, awaiting in faith with Our Blessed Mother, as we trust entirely in God, who loves us more than we can ever know.