Pentecost
Whitsunday

Pentecost, also known as Whitsunday, is celebrated fifty days following Easter Sunday and ten days after Ascension Day. It commemorates the coming of the Holy Spirit:

And when the day of Pentecost was fully come, they were all with one accord in one place. And suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the house where they were sitting. And there appeared unto them cloven tongues like as of fire, and it sat upon each of them. And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.

Acts 2:1-4

This happened on the Jewish festival of Pentecost or Shavuot, the Festival of the Giving of the Law, which commemorates Moses receiving the Ten Commandments on Mount Sinai after leaving Egypt.

Some Christians believe that Pentecost is the birth of the Church because Peter preached his first sermon after the Gift of the Holy Spirit and over 3,000 people became believers in the Christian faith.