Pentecost….
Christianity By The Editors of Encyclopaedia Britannica
Pentecost for the year 2023 is celebrated/ observed on Sunday, May 28th.
Pentecost is celebrated on the seventh Sunday or 50 days after Easter Sunday
Pentecost, also called Whitsunday, (Pentecost from Greek pentecostē, “50th day”), major festival in the Christian church, celebrated on the Sunday that falls on the 50th day of Easter. It commemorates the descent of the Holy Spirit on the Apostles and other disciples following the Crucifixion, Resurrection, and Ascension of Jesus Christ (Acts of the Apostles, chapter 2), and it marks the beginning of the Christian church’s mission to the world.
The Jewish feast of Pentecost (Shavuot) was primarily a thanksgiving for the firstfruits of the wheat harvest, but it was later associated with a remembrance of the Law given by God to Moses on Mount Sinai. The church’s transformation of the Jewish feast to a Christian festival was thus related to the belief that the gift of the Holy Spirit to the followers of Jesus was the firstfruits of a new dispensation that fulfilled and succeeded the old dispensation of the Law.
When the festival was first celebrated in the Christian church is not known, but it was mentioned in a work from the Eastern church, the Epistola Apostolorum, in the 2nd century. In the 3rd century it was mentioned by Origen, theologian and head of the catechetical school in Alexandria, and by Tertullian, Christian priest and writer of Carthage.
In the early church, Christians often referred to the entire 50-day period beginning with Easter as Pentecost. Baptism was administered both at the beginning (Easter) and end (the day of Pentecost) of the Paschal season. Eventually, Pentecost became a more popular time for baptism than Easter in northern Europe, and in England the feast was commonly called White Sunday (Whitsunday) for the special white garments worn by the newly baptized. In The First Prayer Book of Edward VI (1549), the feast was officially called Whitsunday, and this name has continued in Anglican churches. In Catholic and other Western churches, priests often wear red vestments during Pentecost to symbolize the “tongues of fire” that descended on the disciples from the Holy Spirit; members of the congregation also wear red in some traditions, and the altar is commonly dressed in a red frontal cloth.
Pentecost
From Wikipedia, the free encyclopedia 
The Christian holiday of Pentecost is celebrated on the 50th day (the seventh Sunday) from Easter Sunday. It 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).
The holiday is also called “Whit Sunday”, “Whitsunday” or “Whitsun“, especially in the United Kingdom, where traditionally the next day, Whit Monday, was also a public holiday (since 1971 fixed by statute on the last Monday in May). The Monday after Pentecost is a legal holiday in many European countries.
In Eastern Christianity, Pentecost can also refer to the entire fifty days of Easter through Pentecost inclusive; hence the book containing the liturgical texts is called the “Pentecostarion“. Since its date depends on the date of Easter, Pentecost is a “moveable feast“.
Pentecost is one of the Great feasts in the Eastern Orthodox Church, a Solemnity in the Roman Rite of the Catholic Church, a Festival in the Lutheran Churches, and a Principal Feast in the Anglican Communion. Many Christian denominations provide a special liturgy for this holy celebration.
Background
In Judaism the Festival of Weeks (Hebrew: שבועות Shavuot) is a harvest festival that is celebrated seven weeks and one day after the first day of Passover (the Feast of Unleavened Bread) in Deuteronomy 16:9 or seven weeks and one day after the Sabbath referred to in Leviticus 23:16. The Festival of Weeks is also called the feast of Harvest in Exodus 23:16 and the day of first fruits in Numbers 28:26. In Exodus 34:22 it is called the “firstfruits of the wheat harvest.” The date for the “Feast of Weeks” originally came the day after seven full weeks following the first harvest of grain. In Jewish tradition the fiftieth day was known as the Festival of Weeks. The actual mention of fifty days comes from Leviticus 23:16.
During the Hellenistic period, the ancient harvest festival also became a day of renewing the Noahic covenant, described in Genesis 9:8-17, which is established between God and “all flesh that is upon the earth”. By this time, some Jews were already living in Diaspora. According to Acts 2:5-11 there were Jews from “every nation under heaven” in Jerusalem, possibly visiting the city as pilgrims during Pentecost. In particular the hoi epidemountes (οἱ ἐπιδημοῦντες) are identified as “visitors” to Jerusalem from Rome. This group of visitors includes both Jews and “proselytes” (προσήλυτος, prosēlytos); sometimes translated as “converts to Judaism”, proselyte referred to non-Jews who adhered fully to the Mosaic laws, including circumcision. The list of nations represented in the biblical text includes Parthians, Medes, Elamites, Mesopotamia, Judaea, Cappadocia, Pontus, Asia, Phrygia, Pamphylia, Egypt, Cyrene, and those who were visiting from Rome. 
After the destruction of the Temple in 70 AD offerings could no longer be brought to the Temple and the focus of the festival shifted from agriculture to the Israelites receiving the Torah (the Five Books of Moses or the Law at Sinai). It became customary to gather at synagogue, stay up all night learning Torah, and reading from the Torah the Ten Commandments and the Israelites acceptance of and promise to live by the Torah.
Acts Pentecost by Julius Schnorr von Carolsfeld
The events of Acts Chapter 2 are set against the backdrop of the celebration of Pentecost in Jerusalem. There are several major features to the Pentecost narrative presented in the second chapter of the Acts of the Apostles. The author begins by noting that the disciples of Jesus “were all together in one place” on the “day of Pentecost” (ἡμέρα τῆς Πεντηκοστῆς). The verb used in Acts 2:1 to indicate the arrival of the day of Pentecost carries a connotation of fulfillment.
There is a “mighty rushing wind” (wind is a common symbol for the Holy Spirit) and “tongues as of fire” appear. The gathered disciples were “filled with the Holy Spirit, and began to speak in other tongues as the Spirit gave them utterance”. Some scholars have interpreted the passage as a reference to the multitude of languages spoken by the gathered disciples, while others have taken the reference to “tongues” (γλῶσσαι) to signify ecstatic speech. In Christian tradition, this event represents fulfillment of the promise that Christ will baptize his followers with the Holy Spirit. (Out of the four New Testament gospels, the distinction between baptism by water and the baptism by Christ with “Holy Spirit and fire” is only found in Matthew and Luke.)
The narrative in Acts evokes the symbolism of Jesus’ baptism in the Jordan River, and the start of his ministry, by explicitly connecting the earlier prophecy of John the Baptist to the baptism of the disciples with the Holy Spirit on the day of Pentecost. The timing of the narrative during the law giving festival of Pentecost symbolizes both continuity with the giving of the law, but also the central role of the Holy Spirit for the early church. The central role of Christ in Christian faith signified a fundamental theological separation from the traditional Jewish faith, which was grounded in the Torah and Mosaic Law.
Peter’s sermon in Acts 2:14–36 stresses the resurrection and exaltation. In his sermon, Peter quotes Joel 2:28–32 and Psalm 16 to indicate that first Pentecost marks the start of the Messianic Age. About one hundred and twenty followers of Christ (Acts 1:15) were present, including the Twelve Apostles (Matthias was Judas‘ replacement) (Acts 1:13, 26), Jesus’ mother Mary, other female disciples and his brothers (Acts 1:14). While those on whom the Spirit had descended were speaking in many languages, the Apostle Peter stood up with the eleven and proclaimed to the crowd that this event was the fulfillment of the prophecy. In Acts 2:17, it reads: “‘And in the last days,’ God says, ‘I will pour out my spirit upon every sort of flesh, and your sons and your daughters will prophesy and your young men will see visions and your old men will dream dreams.” He also mentions (Acts 2:15) that it was the third hour of the day (about 9:00 am). Acts 2:41 then reports: “Then they that gladly received his word were baptized: and the same day there were added unto them about three thousand souls.” Critical scholars believe some features of the narrative are theological constructions. Scholars believe that even if the Pentecost narrative is not literally true, it does signify an important event in the history of the early church which enabled the rapid spread of Christianity. Within a few decades important congregations had been established in all major cities of the Roman Empire. 
Biblical commentator Richard C. H. Lenski has noted that the use of the term “Pentecost” in Acts is a reference to the Jewish festival. He writes that a well-defined, distinct Christian celebration did not exist until later years, when Christians kept the name of “Pentecost” but began to calculate the date of the feast based on Easter rather than Passover.
Peter stated that this event was the beginning of a continual outpouring that would be available to all believers from that point on, Jews and Gentiles alike
Western Churches
In some Evangelical and Pentecostal churches, where there is less emphasis on the liturgical year, Pentecost may still be one of the greatest celebrations in the year, such as in Germany or Romania. In other cases, Pentecost may be ignored as a holy day in these churches. In many evangelical churches in the United States, the secular holiday, Mother’s Day, may be more celebrated than the ancient and biblical feast of Pentecost. Some evangelicals and Pentecostals are observing the liturgical calendar and observe Pentecost as a day to teach the Gifts of the Holy Spirit.
Across denominational lines Pentecost has been an opportunity for Christians to honor the role of the Holy Spirit in their lives, and celebrate the birth of the Christian Church in an ecumenical context.
Red Symbolism
A Protestant church altar, decorated for Pentecost with red burning candles and red banners and altar cloth depicting the movement of the Holy Spirit.
The main sign of Pentecost in the West is the color red. It symbolizes joy and the fire of the Holy Spirit.
Priests or ministers, and choirs wear red vestments, and in modern times, the custom has extended to the lay people of the congregation wearing red clothing in celebration as well. Red banners are often hung from walls or ceilings to symbolize the blowing of the “mighty wind” and the free movement of the Spirit.
In some cases, red fans, or red handkerchiefs, are distributed to the congregation to be waved during the procession, etc. Other congregations have incorporated the use of red balloons, signifying the “Birthday of the Church”. These may be borne by the congregants, decorate the sanctuary, or released all at once.