October 1 is the Feast of the Protection of the Mother of God, which is honored in the Byzantine Rite and considered a major holy day among Slavic Christians.
The Feast of the Protection of the Mother of God (Pokrov) celebrates the 10th Century appearance of the Blessed Virgin Mary at the Church of Blachernae, formerly located northwest of Constantinople (Istanbul). According to tradition, St. Andrei of Constantinople -- considered a "Fool for Christ" -- and his disciple Epiphanius witnessed an apparition of the Mother of God above where relics of her robe, veil, and belt were kept in the church. After kneeling down in prayer, the Blessed Virgin then removed her veil and spread it over the people in the church as a sign of her unwavering protection. Because St. Andrei was a Slav, the commemoration of this event spread quickly among his people.
For Slavic Catholics who use the Byzantine Rite, Pokrov is kept as a Vigil-rank feast. This means, at least in monastic settings, the feast is celebrated with the All-Night Vigil, a solemn liturgical service that combines Vespers, Matins, and the First Hour (Prime). Many parishes honor the feast with Greast Vespers on September 30, followed by the Divine Liturgy the next day. Over the centuries, various Eastern Chrisitan populations have attributed protection from and victory over invading forces to the Mother of God's protection.
The following are the troparion and kontakion (primary hymns) of Pokrov. And though the Feast of the Protection of the Mother of God is rooted in the Byzantine tradition, all Catholics are welcome to honor the Blessed Virgin's many graces and seek her protection whenever they are in need.
Today the faithful celebrate the feast with joy
illumined by your coming, O Mother of God.
Beholding your pure image we fervently cry to you:
"Encompass us beneath the precious veil of your protection;
deliver us from every form of evil by entreating Christ,
your Son and our God that He may save our souls.
Today the Virgin stands in the midst of the Church
and with choirs of saints she invisibly prays to God for us.
Angels and bishops worship,
apostles and prophets rejoice together,
since for our sake she prays to the pre-eternal God.