The month of May is the "month which the piety of the faithful has especially dedicated to Our Blessed Lady," and it is the occasion for a "moving tribute of faith and love which Catholics in every part of the world [pay] to the Queen of Heaven. During this month Christians, both in church and in the privacy of the home, offer up to Mary from their hearts an especially fervent and loving homage of prayer and veneration. In this month, too, the benefits of God's mercy come down to us from her throne in greater abundance" (Paul VI: Encyclical on the Month of May, no. 1).
This Christian custom of dedicating the month of May to the Blessed Virgin arose at the end of the 13th century. In this way, the Church was able to Christianize the secular feasts which were wont to take place at that time. In the 16th century, books appeared and fostered this devotion.
In May of 2002, Pope John Paul II said, "Today we begin the month dedicated to Our Lady a favorite of popular devotion. In accord with a long-standing tradition of devotion, parishes, and families continue to make the month of May a 'Marian' month, celebrating it with many devout liturgical, catechetical, and pastoral initiatives!"