Per the USCCB: This prayer to Saint Joseph—spouse of the Virgin Mary, foster father of Jesus, and patron saint of the universal Church—was composed by Pope Leo XIII in his 1889 encyclical, Quamquam Pluries. . .. He asked that it be added to the end of the Rosary, especially during the month of October, which is dedicated to the Rosary. The prayer is enriched with a partial indulgence (Handbook of Indulgences, conc. 19), and may be said after the customary Salve Reginaand concluding prayer. It may also be used to conclude other Marian devotions.