One of the lesser-known Marian feast days in October is the Feast of the Purity of the Blessed Virgin Mary. Previously this was celebrated in some places on the Third Sunday in October, but after the reforms of Pope St. Pius X, it was moved to October 16th every year.
The Feast of the Purity of the Blessed Virgin Mary is not on the universal calendar. Therefore, you may have never heard of it and there is a great chance that you would not see it celebrated at your local parish. However, it has always been celebrated by the Carmelite Order due to their particular devotion to Our Blessed Lady.
And because of the Carmelite connection with the Brown Scapular, we thought it could be helpful to mention it here. The Church has many particular devotions to Our Lord and Our Lady scattered throughout the Church calendar, and even if we don't see them celebrated in all places, we can still learn about them and pray to Our Lady under these titles as a sign of our devotion.
Hail holy Mother, thou didst bring forth the King, who ruleth heaven and earth for ever and ever. My heart hath uttered a good word: I speak my works to the King - Sedulius, and Psalm 44:2 from the Introit of Mass
Grant we beseech Thee, almightly everlasting God: that, as we venerate with festal celebration the most complete Virginity of the most pure Virgin Mary, we may attain purity of mind and body - Collect