Pentecost Sunday is one of the most ancient feasts of the Church, celebrated early enough to be mentioned in the Acts of the Apostles (20:16) and St. Paul’s First Letter to the Corinthians (16:8). It is the 50th day after Easter (counting both Easter and Pentecost).Bringing the Paschal Mystery to completion, God bestows the Holy Spirit today on those He made His adopted children by uniting them to His Only Begotten Son. This same Spirit, as the Church came to birth, opened to all peoples the knowledge of God and brought together many languages of the earth in profession of the one faith.