The feast day of the Immaculate Heart of Mary falls on the day after the feast of the Sacred Heart of Jesus because devotion to these two hearts was promoted together as a means of entering more deeply into the mystery of God’s love.
In 1944, in the midst of WWII, Pope Pius XII dedicated the entire world to the patronage and protection of the Immaculate Heart of Mary—the intention expressed in his decree was "peace among nations, freedom for the Church, the conversion of sinners, the love of purity and the practice of virtue.”
Though it found prominence in the 20th century, devotion to Mary’s Immaculate Heart is not new. Early Christians revered the movements of Mary’s heart in the Gospels—she pondered the events of the nativity in her heart (Lk 2:19); and when she and Joseph presented Jesus in the temple, Simeon prophesied that a sword of sorrow would pierce her heart (Lk 2:35). Of course, Mary was faithful to Jesus to the end, and the image of her sorrowfully beholding her Son on the cross has always struck a deep chord with the faithful.
Devotion to Mary’s heart was taken up by theologians and saints from many ages, but it was the 17th century French preacher, Saint John Eudes, who formalized this devotion into the liturgical practice that we observe today. Saint John’s spirituality focused on the love of Jesus and Mary, symbolized in their sacred hearts. He began a feast day for parishes in France to encourage people to honor the heart of Mary and the Sacred Heart of Jesus; these feast days spread quickly and were taken up by the Universal Church.
Devotion to the Sacred Heart of Jesus focuses on God’s immense love for humanity, even though it was repulsed, scorned, and crucified. Devotion to the Immaculate Heart of Mary points us towards her love for Jesus and for God as an example.
Since the reform of the liturgical calendar in 1969 moved this feast to the Saturday after the feast of the Sacred Heart, we should think about making reparation also for the offenses done to the Heart of Mary.
Adapted from Faith