It is celebrated 49 days after Holy Easter.
“On this day, the eighth Sunday from Easter, we celebrate Holy Pentecost. Violent tongue-burning breath blows, Christ the divine Spirit to the Apostles. A great fishing Spirit emerges. The embassies of the holy Apostles, Christ our God, have mercy on us. Amen”
After the Lord’s Ascension into heaven, the Apostles and the rest of his disciples, as well as the women who had followed him from the beginning, the Virgin Mary his Mother, about 120 people, returned to the Mount of Olives in Jerusalem and, entering in the porch, that is, on the upper floor of the house there, they waited with prayer for the indwelling of the Holy Spirit, according to the promise of Christ the Savior. In the meantime there, they also chose Matthias and numbered him with the eleven Apostles.
Then they, filled by the Holy Spirit, began to preach and call people to be baptized and receive the grace of the Holy Spirit. What they had heard and lived close to Christ and did not understand at the time, now in the Holy Spirit they know it and preach it to the people.
Now they know what the perspective of the new life is and where they must lead the people, that is why they lead the first three thousand who were baptized to the Supper of Life, the Table of the Eucharist, where the Church will henceforth be gathered as body of Christ, will be nourished with the Body and Blood of the Lord and will thus participate in the eternal life of the Kingdom of God.
With Pentecost, the Church was not born as a simple institution, but as a continuous presence of the grace of the Holy Spirit, and that is why Pentecost is not an event that happened once, but is the life of the Church, as a continuous communion of the Holy Spirit .
Pentecost is the birthday of the Church.