Following the predecessors, Pope Blessed John Paul II wrote and spoke much about Mary and the Rosary. On March 25,1987, he issued an Encyclical entitled Redemptoris Mater (“The Mother of the Redeemer”), dealing with the Blessed Virgin in the life of the Church on her pilgrimage of faith.
On October 16, 2002, the Pope issued an Apostolic Letter entitled Rosarium Virginis Mariæ (“The Rosary of the Virgin Mary”) which provided an in-depth look at this time-honored Marian devotion and broadened the Mysteries that are contemplated in its recitation.
The late Pope suggested the addition of the five new Mysteries from events found in the Public Ministry of Jesus, between his Passion, a part of his life that was not covered by contemplation of the traditional Mysteries. He wrote:
“In the course of [the new] Mysteries we contemplate important aspects of the person of Christ as the definitive revelation of God. Declared the beloved Son of the Father at the Baptism in the Jordan, Christ is the one who announces the coming of the Kingdom, bears witness to it in his works, and proclaims its demands. It is during the years of his public ministry that the Mystery of Christ is most evidently a Mystery of Light: ‘While I am in the world, I am the light of the world’ (John 9:5).
“Consequently, for the Rosary to become more fully a compendium of the gospel’ it is fitting to add following reflection on the Incarnation and the hidden life of Christ (the joyful mysteries) and the triumph of his Resurrection (the Glorious Mysteries) a meditation on certain particularly significant moments in his public ministry (the Mysteries of Light or the Luminous Mysteries).
The people listed five new Mysteries of Christ, making a total of twenty instead of the customary fifteen: (1) His Baptism in the Jordan, (2) His self-manifestation at the Wedding of Cana, (3) His Proclamation of the Kingdom of God, (4) His Transfiguration and (5) His Institution of the Eucharist.
In doing so, the Pope made it possible for us to bring our prayer life into closer touch with the Liturgical Year. It is true, of course, that we can say the Rosary simply without reference to any day, month, or season in the Liturgical Year. However, the Church is on record as saying that private or semiprivate prayers should proceed in accord with the major themes of the Liturgical Seasons.
These new Mysteries enable us to say the Rosary in accord with every season. We now, so to speak, have the Mysteries that go with Ordinary Time, which previously where lacking. (From The Greatest Marian Titles by Anthony Buono)