The Christian holiday of Pentecost, which is celebrated on the seventh Sunday after Easter, 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). In Christian tradition, this event represents the birth of the early Church.

The holy day is also called "White Sunday" or "Whitsunday", bespecially in the United Kingdom, where traditionally the next day, Whit Monday, was also a public holiday (now fixed by statute on the last Monday in May). The Monday after Pentecost is a legal holiday in many European nations.

From Wikipedia