Pentecost is considered the birthday of the Christian Church. Fifty days after Easter, Christians mark the Descent of the Holy Spirit on the Apostles. Christ promised his disciples that he would send them another Comforter, which according to the Bible happened in Jerusalem behind closed doors, when the disciples heard the sound of a wind and saw flames as if of fire descend upon them. On that day, 3,000 people were baptised. The feast is based on the beginning of the Acts of the Apostles. Throughout most of Christianity, Pentecost is still a two-day feast.
Pentecost is one of the 24 major liturgical feasts of the Catholic Church.