The Christian holiday of Pentecost, which is celebrated the 50th day (the seventh Sunday) after Easter Sunday, commemorates the descent of the Holy Spirit upon the Apostles and other followers of Jesus Christ while they were in Jerusalem celebrating the Feast of Weeks, as described in the Acts of the Apostles (Acts 2:1-31).
Pentecost falls on the 50th day after the resurrection of Jesus.
On Pentecost Sunday, we remember the day the disciples received the Holy Spirit in a special way. The story in Acts 2 describes a powerful wind and tongues of fire as the Holy Spirit was poured out on people from all over the world who came to Jerusalem to celebrate a Jewish feast. At the first Pentecost over 3000 people were baptized, creating the first church. This is why Pentecost is known as the birthday of the Christian church.
The Season after Pentecost is the time of the church year to support new disciples and the whole congregation in living out the gifts we have been given in the name of Jesus and the power of the Holy Spirit.