The Day of Pentecost is an important Christian holiday celebrated fifty days after Easter. It marks the day that the Holy Spirit descended upon the Apostles, as described in the Bible in Acts 2. The day is celebrated with special services, readings, and prayers. The day is also known as Whitsunday, or White Sunday, as the tradition is for worshippers to wear white clothing to symbolize the purity of the Holy Spirit. Pentecost is a day of joy and celebration, as it marks the beginning of the Christian church and the spread of the Gospel.