The descent of the Holy Spirit upon the Apostles fifty days after Pascha, marking the full revelation of the Holy Trinity and the beginning of the Church's mission in the world. During Vespers, special kneeling prayers are offered and the church is adorned with greenery. This feast celebrates the completion of Christ's saving work and the outpouring of the Holy Spirit upon all believers. From this day forward, the Sundays of the year are numbered from Pentecost, signifying the continual life and growth of the Church in the grace of the Spirit.

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 beginning of the Orthodox liturgical year on September 1st. Also called the Indiction, this feast marks the start of the annual cycle of feasts and fasts. Many Orthodox churches hold special services with prayers for the new year, blessing of schools, and remembrance of God's creation. It emphasizes new beginnings and spiritual renewal.

The celebration of the birth of the Virgin Mary to Saints Joachim and Anna. This feast, observed on September 8th, marks the beginning of our salvation history, as Mary's birth prepared the way for the Incarnation. The Church honors Mary as the bridge between the Old and New Testaments.

The commemoration of the finding of Christ's Cross by St. Helena and its elevation by St. Macarius for veneration. Celebrated on September 14th, this feast is both joyful (for the Cross's discovery) and solemn (remembering Christ's suffering). Flowers and basil are often blessed, and a strict fast is observed.

The commemoration of the Virgin Mary's miraculous appearance in Constantinople, when she spread her veil over the praying Christians to protect them from enemies. Celebrated on October 1st, this feast is especially beloved in Slavic Orthodox churches. It emphasizes the Theotokos's continuing intercession and protection of the faithful.