The Christian Liturgy is a ceremony that Christians perform on their holy days and feast days. It is an active expression of God's will, worked out through His only Begotten Son, Jesus Christ of Nazareth.
The chief purpose of this main Liturgy is to enable participants to partake of the sacraments of bread and wine, the body and blood of Jesus Christ. In carrying out this rite, participants are giving due reverence to God the Almighty who is the ultimate source of it and to the Holy Spirit that makes Christ's presence real in it.
Pentecost, originally a celebration of the Jews, became a sacred Christian day after the outpouring of God's Holy Spirit upon Christ's first disciples. This event took place after Christ had ascended into heaven. Pentecost probably was not formally celebrated in liturgy as a Feast Day until the time of Constantine the Great; and it remains the second most important Feast in the Christian Liturgical calendar after Easter, for it was because of the Holy Spirit outpouring that Christ's Church was established and His followers were empowered to do God's will.
Liturgical rites during the Pentecostal season have undergone many transitions, but the rite of Holy Communion [the Eucharist] has remained the same. This major rite is always performed in conjunction with all the other liturgical rites during this time.
Etymology and Definition
Liturgy comes from the Late Latin word "liturgia" and from the Greek word "leitourgia" [public service].
Merriam Webster defines Liturgy [Liturgua] as (1) a Eucharistic rite,(2) a rite or body of rites prescribed for public worship, a customary repertoire of ideas, phrases, or observances.
There are different terms for the Christian Liturgy although it was the same Liturgy instituted by Jesus Christ in 33AD during His Last Super. [Note that this Liturgy sets the pattern for worship by Christian congregations.]
"Divine Liturgy" is the common term used for the Eucharistic service of the Byzantine tradition of Christian liturgy. As such, it is used in the Eastern Orthodox and Eastern Catholic Churches.
"Mass" is the common term used for the Liturgy service or the Eucharistic celebration in the Latin liturgical rites of the Roman Catholic Church.
"Eucharist," "Holy Communion" and "The Lord's Supper" refer to the sacraments of bread and wine that were given by Jesus to His 12 Apostles during His Last Supper. The phrase "the Eucharist", however, can refer to the actual rite that Jesus performed or to the sacraments themselves. When referring to the sacraments, communicants speak of "receiving the Eucharist" rather than "celebrating the Eucharist." 
The Lord's Last Supper rite will be referred to as "The Divine Liturgy", "Mass", the "Eucharist" or "Communion" where appropriate.
The format of the Divine Liturgy is fixed, although the specific readings and hymns vary from one season to another. The Liturgy always consists of three interrelated parts:The Liturgy of Preparation, which includes the entry and vesting prayers of the clergy and the Prothesis; The Liturgy of the Catechumens, so called because in ancient times catechumens were allowed to attend;The Liturgy of the Faithful, so called because in ancient times only faithful members in good standing were allowed to participate.[In modern times, this restriction applies only to receiving of the sacraments.]
According to the The Roman Catholic Church, the Eucharist is seen as one of the seven sacraments. The institution of the Eucharist is one of the Luminous Mysteries of the Rosary. It commemorates the Passion, Death, and Resurrection of Christ. 
The Eastern Orthodox Church affirms the Real Presence in the consecrated bread and wine which they believe to be the actual Body and Blood of Jesus Christ. The Eastern Orthodox Church has never described exactly how this occurs, nor has it ever gone into the detail that the Roman Catholic Church has with the doctrine of transubstantiation. This doctrine was formulated after the Great Schism took place, and the Eastern Orthodox churches have never formally affirmed or denied it, preferring to call it a "Mystery".
The Anglican Church maintains its historical position on Holy Communion as found in the Thirty-Nine Articles of 1571, which state "the Bread which we break is a partaking of the Body of Christ"; and likewise that "the Cup of Blessing is a partaking of the Blood of Christ" (Articles of Religion, Article XXVIII: Of the Lord's Supper). 
Ignatius of Antioch, one of the Apostolic Fathers, mentions the Eucharist as "the flesh of our Saviour Jesus Christ".
Early Accounts of The Divine Liturgy [the Lord's Last Supper]
Apostle Paul's Account
In his First Epistle to the Corinthians (c 54-55), the Apostle Paul gives the earliest recorded description of Jesus' Last Supper. Paul states that "The Lord Jesus on the night when he was betrayed, took bread, and when he had given thanks, he broke it, and said, 'This is my body which is for you. Do this in remembrance of me.' In the same way also the cup, after supper, saying, 'This cup is the new covenant in my blood. Do this, as often as you drink it, in remembrance of me'" [1 Corinthians 11:23–24]. Paul's account is in keeping with the Lord Jesus' account in Matthew where He says, concerning the bread, "...Take and eat; this is my body." And concerning the wine, "...Drink from it, all of you.This is my blood of the covenant, which is poured out for many for the forgiveness of sins."
Paul also denounced the way in which the Lord's Supper was celebrated at Corinth. Middle and upper-class people who could come early to the meetings of the Christians feasted on the better food and drink in a way that shamed the slaves and peasants who could arrive only later. He pointed out that they were all were participating in Christ's body and blood, not their own meal, and to do so in an unworthy manner, with divisions and class distinctions among them, profaned the meal, turning it from the Lord's Supper to a sham.
Justin Martyr's Account
The earliest surviving account of the celebration of the Divine Liturgy in Rome is that of Saint Justin Martyr (died c. 165). In chapter 67 of his First Apology , he states that "On the day called Sunday, all who live in cities or in the country gather together to one place, and the memoirs of the apostles or the writings of the prophets are read,...when the reader has ceased, the president verbally instructs, and exhorts to the imitation of these good things. Then we all rise together and pray, and, as we before said, when our prayer is ended, bread and wine and water are brought, and the president in like manner offers prayers and thanksgivings, according to his ability, and the people assent, saying Amen; and there is a distribution to each, and a participation of that over which thanks have been given, and to those who are absent a portion is sent by the deacons."
Origin of the Divine Liturgy
Divine Origin and Location
As mentioned earlier, the Divine Liturgy is the The Lord's Supper, and was instituted by Jesus Christ of Nazareth in 33 A.D. This sacred event occurred on the first night of Passover, Nisan 14, the time of the Jewish Passover Seder in accordance with the Mosaic tradition.
It took place in what is called today, "The Room of the Last Supper" [The Upper Room], situated on Mount Zion, just outside of the walls of the Old City of Jerusalem. This information is based on the account in the Gospels which states that Jesus had instructed a pair of His disciples to go to the city whereby they would encounter a man carrying a jar of water. He told them that this man would lead them to a house where the teacher had a guest room -- and they were to ask for this room. The Last Supper appears in all three Synoptic Gospels: Matthew, Mark, and Luke; and in the First Epistle to the Corinthians.
[The traditional location of the house is an area that, according to archaeology, had a large Essene community, adding to the belief that there was a link between Jesus and this group (Kilgallen 265). 
History reveals, that after the destruction of Jerusalem in 70 AD, the early Christians who had fled to Pella, came back and congregated in the house of John Mark and his mother Mary, the place where they had met before (Acts 12:12 sq.). This was apprently the house of where the Last Supper and the outpouring of the Holy Spirit at Pentecost took place. Epiphanius (d. 403) says that when the Emperor Hadrian came to Jerusalem in 130 he found the Temple and the whole city destroyed save for a few houses, among them the one where the Apostles had received the Holy Ghost. This house, says Epiphanius, is "in that part of Sion which was spared when the city was destroyed" -- in the "upper part" ("De mens. et pond.", cap. xiv). From the time of Cyril of Jerusalem, who speaks of "the upper Church of the Apostles, where the Holy Ghost came down upon them" (Catech., ii, 6; P. G., XXXIII), there are abundant witnesses of the place. It is the famous Coenaculum or Cenacle -- now a Moslem shrine -- near the Gate of David, and supposed to be David's tomb (Nebi Daud).
Christ's Apostles and their followers first preserved the Jewish custom of going to the Temple at the hour of prayer. But they had also their reunions in private houses for the celebration of the Eucharist and for sermons and exhortations. These Eucharistic assemblies or reunions soon entailed other prayers. As the custom of going to the Temple disappeared, and as the early Christians separated more distinctly from the Jews and their practices and forms of worship, the celebration of the Lord's Last Supper ceased to borrow from Judaism. 
Sources reveal that the Lord's Last Supper ritual was performed regularly by Christ's Apostles in the early Church as a prayer or blessing over the holy sacraments, bread and wine, and was followed by a common meal. 
Early Treatises on Liturgical Rites
The Didache [di' də ki ], a Greek teaching of the first century Christian church, contained instructions for Christian worship for the growing communities. Its contents may may be divided into three parts: (1) "The Two Ways: the 'The Way of Life' and 'The Way of Death'"; (2) a rituale dealing with baptism, fasting, and Holy Communion; (3) the ministry. It was written by Christ's twelve Apostles and has been dated to the late first - early second century AD.
Chapter IX of the Second Part of the Didache [the rituale] on the service of the Eucharist states: "Concerning the Eucharist, thus shall you give thanks: 'We give Thee thanks, our Father, for the holy Vine of David Thy Child, which Thou hast made known to us through Jesus Thy Child; to Thee be the glory forever'. And of the broken Bread: 'We give Thee thanks, our Father, for the Life and knowledge which Thou hast made known to us through Jesus Thy Child; to Thee be glory for ever. For as this broken Bread was dispersed over the mountains, and being collected became one, so may Thy Church be gathered together from the ends of the earth into Thy kingdom, for Thine is the glory and the power through Jesus Christ for ever.' And let none eat or drink of your Eucharist but those who have been baptized in the Name of Christ; for of this the Lord said: 'Give not the holy Thing to the dogs'." These are clearly prayers after the Consecration and before Communion. Chapter X gives a thanksgiving after Communion, slightly longer, in which mention is made of the "spiritual food and drink and eternal Life through Thy Child".
The Liturgy of the Apostolic Constitutions
The oldest known form that can be described as a complete liturgy is that of the Apostolic Constitutions. It is also the first member of the line of Antiochene uses. The Apostolic Constitutions consist of eight books purporting to have been written by St. Clement of Rome (died c. 104). The first six books are an interpolated edition of the Didascalia ("Teaching of the Apostles and Disciples"), written in the first half of the third century and since edited in a Syriac version by de Lagarde, 1854); the seventh book is an equally modified version of the Didache (Teaching of the Twelve Apostles,) with a collection of prayers. The eighth book contains a complete liturgy and the eighty-five "Apostolic Canons". 
The Liturgy of Saint James
According to one source, "The Divine Liturgy of St James the Just, which was until recently only celebrated on the island of Zakynthos, on his feast day of October 23rd and in Jerusalem on the Sunday after Christmas, is today celebrated in increasing numbers by Orthodox churches. It was the ancient rite of Jerusalem, as the Mystagogic Catecheses of St Cyril of Jerusalem imply. The Liturgy of Saint James, in its Syrian form, is the principal liturgy of The Syrian Oriental Church and the ancient Syrian Orthodox Church of India today." Jdgray 16:14, 20 August 2008 (UTC)
The Byzantine Rite [The Rite of Constantinople]
The Liturgies, Divine Office, forms for the administration of sacraments, etc. of the Church of Constantinople, is by far the most widely spread in the world after the Roman Rite. This means that hundreds of millions of Christians perform their devotions according to the Rite of Constantinople.
The Rite of Constantinople, however, is not one of the original parent-rites but is derived from that of Antioch. Even apart from the external evidence, a comparison of the two liturgies will show that Constantinople follows Antioch in the disposition of the parts. [See "The Rite of Constantinople: History"]. 
The Divine Liturgy of Saint Basil the Great/the Divine Liturgy of St. John Chrysostom
St. Basil's liturgy had as its source, the Greek Liturgy of St. James. The original rite that stands at the head of this line of development is that of Antioch. Before the rise of the Patriarchate  of Constantinople, Antioch was the head of the Churches of Asia Minor as well as of Syria; and in the East. This fact is proven from the disposition of the present Liturgy of St. Basil.http://www.goarch.org/en/chapel/liturgical_texts/basil.asp#divine
Saint Basil of Caesarea came at the end of the age of persecution. At this time, liturgical prayers were in a state of transition. Once memorized, they were then made into written formulas and starting to become influenced by court ritual. [Note: The Divine Liturgy of St. John Chrysostom is traditionally thought to be a shortened form of the Divine Liturgy of St. Basil. Both are related to the earlier Divine Liturgy of St. James the Just, brother of the Lord Jesus Christ, first Bishop of Jerusalem.
Also see Kurbānā (Eucharistic Divine Liturgy). Jdgray 13:00, 30 September 2008 (UTC)
Book of Common Prayer
The service for the Divine Liturgy [Holy Eucharist] is found in the Book of Common Prayer for each national Church in the Anglican Communion. The Anglican Church holds the Eucharist as the highest form of worship and considers it the Church's main service. 
The Roman Missal
The Roman Missal is the liturgical book that contains the texts and rubrics for the celebration of the Mass in the Roman Rite of the Roman Catholic Church. This missal was produced following the meeting of the Council of Trent. The Council had called for a standardized western rite to be used by every congregation whose current rite was not at least 200 years old, and it entrusted to Pope Pius V the implementation of its work. As a result, Pope Pius issued the Roman Catechism in 1566, a revised Roman Breviary in 1568 and a revised Roman Missal in 1570, thus initiating what has been called in the twentieth century, the Tridentine Mass. 
Many local rites that remained legitimate even after this decree, were abandoned voluntarily, especially in the nineteenth century. And most religious orders that still had kept a rite of their own chose to adopt the reformed Roman Rite as revised in accordance with the decrees of the Second Vatican Council (see Mass of Paul VI). A few such liturgical rites persist today for the celebration of Mass since 1965-1970 in revised forms, but the distinct liturgical rites for celebrating the other sacraments have been almost completely abandoned. 
The Three Stages of Development of the Roman Mass
1st Stage - Pre-Tridentine [before 1570 AD]
Pre-Tridentine Mass refers to the variants of the liturgical rite of Mass in Rome before 1570, when, with his bull Quo primum Pope Pius V made the Roman Missal, as revised by him, obligatory throughout the Latin-Rite or Western Church, except for those places and congregations whose distinct rites could demonstrate a pedigree of 200 years or more.[ http://en.wikipedia.org/wiki/Pre-Tridentine_Mass#Earliest_accounts]
2nd Stage - Tridentine [between 1570 & 1962]
The Mass conducted during the Tridentine stage was in the form of the Roman Rite Mass contained in the typical editions of the Roman Missal published between 1570 and 1962. Other names for it include Traditional Mass, Traditional Latin Mass, and, in its latest form, Mass according to the 1962 Roman Missal.
3rd Stage - Post-Tridentine [1962-1965]
The third and final stage of the development is called Post-Tridentine. The Mass of Pope Paul VI, [the Catholic Mass of the Roman Rite[promulgated by him in 1969 after the Second Vatican Council (1962–1965)] came to be used and is the present ordinary (normal) form of the Roman Rite of the Mass.
The Pentecostarion is the liturgical book used by the Eastern Orthodox and Eastern Catholic Churches which follow the Byzantine Rite during the Paschal Season. This season extends from Pascha (Easter) to the Sunday following All Saints Sunday (the Second Sunday After Pentecost). 
Pentecost (Ancient Greek: πεντηκοστή [ἡμέρα], pentekostē [hēmera], "the fiftieth day") is the Greek name for one of the prominent feasts in the Christian liturgical year, celebrated the 49th day (7 weeks) after Easter Sunday—or the 50th day. It
is derived from the Greek name for Shavuot, one of the three Pilgrimage Festivals required in the Law of Moses, and is mainly described in Leviticus 23:5-21 and Deuteronomy 16:8-10
Origin and Purpose
Pentecost's Hebrew name "khag shavuot" became the best-known name of the feast. For Jews, this feast marked the end of the harvest, and a new "meat offering" was offered unto the Lord. [See Deuteronomy 16:8-10]. Shavuot (or Shavuos, in Ashkenazi usage; Hebrew: שבועות, lit. "Weeks") is known as "the reaping festival". It occurs on the sixth day of the Hebrew month of Sivan (late May or early June)and commemorates the anniversary of the day G-d gave the Ten Commandments to Moses and the Israelites at Mount Sinai. It is one of the three biblical pilgrimage festivals and marks the conclusion of the Counting of the Omer, which is a verbal counting of each of the forty-nine days between the Jewish holidays of Passover and Shavuot.
The Counting of the Omer begins on the second day of Passover [Nisan 15] and ends the day before the holiday of Shavuot [Pentecost], the 'fiftieth day' which immediately follows. In the book of Exodus it says, "And keep the Festival of Shavuot through the first fruits of your wheat harvest."(Exodus 34) 
The Christian observance of Pentecost is rooted in the event of the outpouring of Holy Spirit on the Day of Pentecost in Jerusalem. Their observance of this event in formal liturgy as a Feast Day, didn't begin, as far as records indicate, until around the fourth century AD. The Christian Feast day falls on the tenth day after Ascension Thursday.
As with the ancient Jewish Festival of Shavuot, the Christian Feast entailed reaping - in the former case a reaping of a wheat harvest, in the latter, a reaping of souls for Christ Jesus' kingdom. [See Exodus 23:16]
Like the Jewish Festival, forty-nine days after Christ's ascension, on the 50th day which is Pentecost, the reaping period began. This reaping of the harvest was accomplished only by the outpouring by Christ of the Holy Spirit. The purpose of this event can be discerned in Christ's words to His disciples, when He explained, "...The harvest truly is plenteous, but the labourers are few; Pray ye therefore the Lord of the harvest, that He will send forth labourers into His harvest" [Matthew 9:37-38].
For many Christians, this was the beginning of the establishment of the Church through the labos of the twelve Apostles, and a culmination of the Holy Trinity.
Biblical Recordings of the Christian Pentecost
The strongest authentification of the Day of Pentecost is found in Jesus' words, "But the Comforter [παράκλητος], which is the Holy Ghost [το πνευμα το ‘άγιον], Whom the Father will send in My name, He shall teach you all things, and bring all things to your remembrance, whatsoever I have said unto you" [John 14:26].
This outpouring of God's Holy Spirit is described in Acts 2:1-4. The text says that Jesus' Apostles and other followers were gathered together in prayer when suddenly the Holy Spirit descended upon them in the form of "cloven tongues of fire," with the sound of a mighty rushing wind. The text goes on to say how all began to speak in languages that they did not know. Visitors from the Jewish diaspora were gathered there to observe the Jewish Feast of Pentecost and became astonished after hearing the apostles, whom they knew to be fishermen, speaking praises to God in their alien tongues; and they wondered what this meant. Some even thought that the Apostles were drunk(Acts 2:1-14).
Acts 2 further explains how Peter, upon hearing the remarks about their being drunk, stood up and addressed the crowd. He preached to the people regarding the Old Testament prophecies about the coming of the Holy Spirit. He spoke about Jesus Christ and His death and glorious Resurrection. Great conviction fell upon the people, and they asked the Apostles, "What shall we do?" Peter said to them, "Repent, and let every one of you be baptized in the name of Jesus Christ for the remission of sins; and you shall receive the gift of the Holy Spirit" (Acts 2:38-39).
In his sermon, Peter quoted the 2nd chapter of the Book of Joel who prophesied this event. Peter says, "And it shall come to pass afterward, that I will pour out My spirit upon all flesh; and your sons and your daughters shall prophesy, your old men shall dream dreams, your young men shall see visions;...And it shall come to pass, that whosoever shall call on the name of the LORD shall be delivered"[Joel 2:28-32].[There are three other prophetic texts which speak about the descent of the Holy Spirit: Ezekiel 36:27, Isaiah 44:3 and Joel 3:1-5.]
Christian teachings affirm that the descent of the Holy Spirit signifies the extension of the divine body of Christ in all the believers [John 14:20].
The Bible book of Acts records that on that day about three thousand were baptized and continued daily to hear the teaching of the Apostles as they met together for fellowship, the breaking of bread, and for prayer. Verse 43 states, "...and many wonderful signs and miracles were done through the Apostles." And verse 47 says, "...and the Lord added to the Church daily those who were being saved" [See Acts 2:41-47].
Calendar Sources for Feast Day Celebrations
The Day of Pentecost is formally commemorated in liturgy [as a Feast Day] and solemnized in Christian churches everywhere. Like all the other feast days and holy days, it had to revolve around Pascha or Easter, the most important day for Christians. Pentecost is, therefore, one of the "twelve great feasts", after Easter, in the Christian calendar. [See Table Below].
[The date of Easter was based on the decision of the First Ecumenical Synod held in Nicaea (325)].
The Calendar of Saints
The Calendar of Saints is a traditional Christian method of organizing saints' feast days during a liturgical year. This calendar may be compared with the Roman Missal. 
In accordance with the Byzantine tradition, the ecclesiastical year begins on the first of September and is divided between movable and immovable or fixed holy days. [See "The Calendar of the Orthodox Church" by Dr. Lewis Patsavos, Ph.D.]
A movable feast is a holy day [This could be a feast day or a fast day.] whose date is not fixed to a particular day of the calendar year, but moves in response to the date of Easter, the date of which varies according to a complex formula. Pentecost is a movable feast day.
Movable feasts surrounding Easter
Good Friday — 2 days before Easter
Easter — the date around which the others are placed
Saint Gregory's Day — 3 days after Easter (in Malta)
The Octave of Easter or Divine Mercy Sunday, also known as Low Sunday or Quasimodo — the Sunday after Easter.
Ascension Day — 39 days after Easter
Pentecost — 49 days after Easter (50th day of Easter)
Trinity Sunday — 56 days after Easter (Western Christianity)
The Pentecostarion or Liturgical Book ["Book of 50 Days]
Again, the Pentecostarion, the Book of the "Fifty Days", refers to the period of time from Pascha to Pentecost.
The Paschal Season [Pascha is called Easter Sunday] refers to the great fifty days that go from Easter Sunday to the Sunday following "all saints day [November 1 - "all Hallows Eve -All Saints' Day. ] This cycle is dependent upon the date of Pascha and continues throughout the coming year until the next Pascha.
During the liturgical season of the Pentecostarion, the Gospel of John is read in full, as is the Acts of the Apostles. Both of these books were chosen because of their instructive content.
The two Sacred Mysteries of baptism and chrismation are reflected in the two feasts which mark the beginning and ending points of the Pentecostarion: Pascha [Easter] and Pentecost. Baptism is naturally tied to the Resurrection, according to the Apostle Paul (Romans 6:, 1 Corinthians 15:4, Colossians 2:12). Chrismation, the reception of the Gifts of the Holy Spirit is naturally reflected in Pentecost. Because of this, the imagery of water figures prominently in the hymns of the Pentecostarion.
Modern Celebrations of Pentecost
Pentecost is a traditional time for baptisms. The Sunday of Pentecost is called "Trinity Sunday," the next day is called "Monday of the Holy Spirit," and Tuesday of Pentecost week is called the "Third Day of the Trinity."
In the Eastern Orthodox Church, it is celebrated with an All-Night Vigil consisting of a combination of the three canonical hours of Vespers, Matins, and the First Hour.] on the Eve of the Feast and the Divine Liturgy on the day of the Feast. An extraordinary service called the Kneeling Prayer, is served on the night of Pentecost. This is a Vespers service to which are added three sets of long poetical prayers, the composition of Saint Basil the Great, during which everyone makes a full prostration, touching their foreheads to the floor (prostrations in church having been forbidden from the day of Pascha up to this point).
On the Monday following the [Pentecostal] Feast, the Divine Liturgy is conducted in commemoration of the All-Holy and Life-Creating and All-Powerful Spirit, Who is God, and One of the Trinity, and is of one honor and one essence and one glory with the Father and the Son (From the Synaxarion of the Feast).
Scripture readings for the Orthodox Christian Feast of Pentecost are as follows:
At the Saturday Vespers: Numbers 11:16-17, 24-29; Joel 2:23-32; Ezekiel 36:24-28.
At the Orthros (Matins): John 20:19-23.
At the Pentecost Sunday Divine Liturgy: Acts 2:1-11; John 7:37-52, 8:12.
At the Divine Liturgy on the Monday of the Holy Spirit: Ephesians 5:8-19; Matthew 18:10-20.
Prayer of the Holy Spirit
Heavenly King, Comforter, the Spirit of Truth, everywhere present and filling all things, Treasury of blessings and Giver of life: come and abide in us, cleanse us from every impurity and save our souls, O Good One.
Hymns of the Feast
Apolytikion (Plagal Tone Four)
Blessed are You, O Christ our God, who made fisherman all-wise, by sending down upon them the Holy Spirit, and through them, drawing all the world into Your net. O Loving One, glory be to You.
Kontakion (Plagal Tone Four)
When the Most High came down and confounded tongues of men at Babel, He divided the nations. When He dispensed the tongues of fire, He called all to unity, and with one voice we glorify the Most Holy Spirit. 
In Sweden Pentecost is celebrated rarely. The Saturday is called "Pentecost Eve," and the following Sunday "Pentecost Day." The Monday is called "Second Pentecost Day," but since 2005, it is no longer a public holiday.
The day is known as "Whit Monday" in England, Wales, and Ireland, and is also celebrated in Iceland, Norway, Denmark, The Netherlands, Poland, Belgium, Luxembourg, parts of Switzerland, Germany, Austria and Hungary. Since 1967, however, Whit Monday has not been a public holiday in the United Kingdom; the holiday has been moved to the fixed date of the last Monday in May, which sometimes but by no means always coincides with Whit Monday. Whit Monday also ceased to be a statutory holiday in France in 2005, where the abolishment led to strong protests. Also in Sweden Whit Monday is no longer a holiday and June 6 (Swedish National Day) has become a day off. 
Dates for Pentecost
Eastern | Western
June 23 | May 19
June 15 | June 8
2005 May 15 | June 1
2006 June 4 | June 11
2007 May 27
2008 May 11 | June 15
2009 May 31 | June 7
2010 May 23
2011 June 12
2012 May 27 | June 3
2013 May 19 | June 23
2014 June 8
2015 May 24 | May 31
2016 May 15 | June 19
2017 June 4
Icon of the Feast
The icon of the Feast of Pentecost is known as "The Descent of the Holy Spirit". It is an icon of bold colors of red and gold signifying that this is a great event. At the top of the icon is a semicircle with rays coming from it. The rays are pointing toward the Apostles, and the tongues of fire are seen descending upon each one of them signifying the descent of the Holy Spirit.
In the icon of Pentecost we see the fulfillment of the promise of the Holy Spirit, sent down upon the Apostles who will teach the nations and baptize them in the name of the Holy Trinity. Here we see that the Church is brought together and sustained in unity through the presence and work of the Holy Spirit, that the Spirit guides the Church in the missionary endeavor throughout the world, and that the Spirit nurtures the Body of Christ, the Church, in truth and love.