Pentecost Sunday falls on June 4, where Christians will celebrate the day that Jesus Christ ascended to heaven and when the Holy Spirit blessed all his apostles. The origin of the word "Pentecost" actually relates to the time of this event, rather than the event itself.
The Pentecost can be found in the New Testament in the Book of Acts 2:1-13, where it accounts the time when the Holy Spirit descended upon Jesus Christ' disciples that made them speaks in different tongues. It was also the significant time when Jesus Christ ascended to heaven.
Acts 2:1-4, which described the Pentecost, reads: "Suddenly there came a sound from heaven as of a rushing mighty wind, and it filled all the houses where they were sitting. And there appeared unto them cloven tongues of fire, and it sat upon each of them. And they were all filled with the Holy Spirit and began to speak in other tongues, and the spirit gave them utterance."
There was a little controversy created from the apostles speaking in tongues. At first, the apostles were thought to be drunk because there was a feast held for the Jews that day, and those who spoke in a different language did not understand what they said.
However, those who heard the message of God through the apostles speaking in tongues were convinced of his miracles.
The word Pentecost came from the Greek term, "pentekoste," which actually stands for "fiftieth." Jesus Christ ascending to heaven and the Holy Spirit descending unto the apostles happened on the fiftieth day after Easter Sunday, which is why it is now called Pentecost Sunday.
Christians celebrate Pentecost Sunday by giving praise to God for blessing them with the Holy Spirit. This helped them preach the miracles of God and gave them the courage to spread His word even without the guidance of Jesus Christ.
Pentecost Sunday will be celebrated this year on June 4.