The central worship service of the Orthodox Church, celebrating the Eucharist (Holy Communion). Usually celebrated on Sundays and feast days, the Divine Liturgy consists of the Liturgy of the Word (scripture readings) and Liturgy of the Faithful (Eucharistic prayer and communion). The most common forms are the Liturgies of St. John Chrysostom and St. Basil the Great.

The Apostle and Evangelist John, author of the Fourth Gospel, three Epistles, and Revelation. Known as "the Theologian" for his profound spiritual insights and "the Beloved Disciple" for his closeness to Christ. Celebrated on May 8th, his feast honors his unique witness to Christ's divine nature and his care for the Theotokos.

The "Apostles to the Slavs" who brought Christianity and literacy to Slavic peoples in the 9th century. Celebrated on May 11th, these brothers created the Glagolitic alphabet and translated the Bible and liturgy into Old Church Slavonic. Their missionary work established Orthodox Christianity among the Bulgarians, Moravians, and other Slavic nations.

The first Christian Emperor Constantine the Great and his mother, St. Helen, who found the True Cross. Celebrated on May 21st, this feast honors Constantine's legalization of Christianity and Helen's pilgrimage to the Holy Land. Their work established Christianity's place in the Byzantine Empire and preserved many holy sites.