Pentecost

Pentecost (also called Whit Sunday, Whitsunday or Whitsun) is a Christian holiday that takes place on the 49th day (50th day when inclusive counting is used) after Easter. It commemorates the descent of the Holy Spirit upon the Apostles of Jesus, Mary, and other followers of Christ, while they were in Jerusalem celebrating the Feast of Weeks, as described in the Acts of the Apostles (Acts 2:1–31). Pentecost marks the "Birthday of the Church".

Pentecost is observed in Christianity. The summary above comes from Wikipedia, where you can read about the history and traditions of this observance.

Pentecost falls on Sunday, May 16, 2027. The countdown above updates live, so you always see exactly how many days, hours, and minutes are left.