Feast of the Transfiguration
The Feast of the Transfiguration of Jesus is celebrated by various Christian denominations. The origins of the feast are less than certain and may have derived from the dedication of three basilicas on Mount Tabor. The feast was present in various forms by the 9th century, and in the Western Church was made a universal feast on August 6th by Pope Callixtus III to commemorate the Siege of Belgrade (1456).
In the Syriac Orthodox, Indian Orthodox, Revised Julian calendars within Eastern Orthodoxy, Roman Catholic, Old Catholic, and Anglican churches, the Feast of the Transfiguration is observed on 6 August. In those Orthodox churches which continue to follow the Julian Calendar, August 6 falls on August 19 of the Gregorian Calendar. The Transfiguration is considered a major feast, numbered among the twelve Great Feasts in Orthodoxy. In all these churches, if the feast falls on a Sunday, its liturgy is not combined with the Sunday liturgy, but completely replaces it.
In some liturgical calendars (e.g. the Lutheran and United Methodist) the last Sunday in the Epiphany season (that immediately preceding Ash Wednesday) is also devoted to this event. In the Church of Sweden and the Church of Finland, however, the Feast is celebrated on the seventh Sunday after Trinity, the eighth Sunday after Pentecost.
In the Eastern Orthodox Church, the Transfiguration falls during the Dormition Fast, but in recognition of the feast the fast is relaxed somewhat and the consumption of fish, wine and oil is allowed on this day.
In the Orthodox view the Transfiguration is not only a feast in honor of Jesus, but a feast of the Holy Trinity, for all three Persons of the Trinity are interpreted as being present at that moment: God the Father spoke from heaven; God the Son was the one being transfigured, and God the Holy Spirit was present in the form of a cloud. In this sense, the transfiguration is also considered the "Small Epiphany" (the "Great Epiphany" being the Baptism of Jesus, when the Holy Trinity appeared in a similar pattern).
Grapes are traditionally brought to church to be blessed after the Divine Liturgy on the day of the Transfiguration. If grapes are not available in the area, apples or some other fruit may be brought. This begins the "Blessing of First Fruits" for the year.
The Transfiguration is the second of the "Three Feasts of the Saviour in August", the other two being the Procession of the Cross on August 1 and the Icon of Christ Not Made by Hand on August 16. The Transfiguration is preceded by a one-day Forefeast and is followed by an Afterfeast of eight days, ending the day before the Forefeast of the Dormition.
In Eastern Orthodox theology, the Tabor Light is the light revealed on Mount Tabor at the Transfiguration of Jesus, identified with the light seen by Paul on the road to Damascus.
The Coptic Orthodox Church Celebrates the feast of transfiguration on the 19th of August, which falls as the 13th of Mesri in the Coptic calendar. The feast is considered one of the 7 minor feasts of the church, and is celebrated in the joyful tune.
The Old Catholic Church celebrates the Transfiguration typically on August 6, according to the Roman rite calendar; however, every local Old Catholic Church throughout the world has the option to celebrate this major feast on a different day. The Old Catholic theological view of the Transfiguration shares much in common with the Eastern Orthodox perspective as stated above. Old Catholics also believe that the transfiguration was a major event that revealed the divinity of Christ; that Jesus is indeed the splendor and eikon of the Father. The Transfiguration shows forth humanity in the splendor of its original form when it was united in the life-giving love of the Triune God. This event reveals the possibility of humanity's theosis.
If the Transfiguration falls on a Sunday, it replaces the ordinary liturgical Ordo of the season for Sacred Liturgy.
In the Roman Catholic Church, the Transfiguration was once celebrated locally in various parts of the Catholic world on different days, including August 6, but was not universally recognized. In 1456, the Kingdom of Hungary repulsed an Ottoman invasion of the Balkans by breaking the Siege of Belgrade. News of the victory arrived in Rome on August 6. Given the importance to international politics at that time of such battles between Christian and Muslim nations, in celebration of the victory Pope Callixtus III elevated the Transfiguration to a Feast day to be celebrated in the entire Roman rite.
German Reformation, Church of England, and the Episcopal Church (USA)
After the Reformation the Feast of the Transfiguration was abandoned in Germany, but continued to be observed in Sweden. The Feast of the Transfiguration is retained in the Common Worship lectionary of the Church of England (6th August). The American Book of Common Prayer of 1892 introduced it to Episcopal use, and from there it has been taken into most modern Anglican calendars (sometimes called "The Transfiguration of Our Lord").
Evangelical Lutheran Church in America
The Evangelical Lutheran Church in America observes the Feast of the Transfiguration as the last Sunday after the Epiphany, which is the Sunday immediately preceding Ash Wednesday and the season of Lent.
Reformed Calvinist and Presbyterian
In the Presbyterian Church, The Sunday of The Transfiguration marks the last day of the Epiphany season, on the last Sunday before Ash Wednesday. The inceptive Calvinist tradition rejected all liturgical feasts, including the Feast of the Transfiguration. This, however, does not mean that the Transfiguration itself was ignored by the Calvinists. Calvin's own view on the Transfiguration were far from ambivalent:
- "It might be asked whether it was really Moses and Elijah who were present or whether only their spectres were set before the disciples, just as often the prophets saw visions of absent things. Although there is much to be said on both sides, as they say, yet it seems more likely to me that they really were brought to that place." 
With time, most major feasts were restored to the Reformed ecclesiastical calendar. The Sunday of Transfiguration is now a part the Revised Common Lectionary. Whether it is celebrated liturgically or in the name only, it is left to the discretion of the clergy or Session.
The Book of Common Worship of 1993 (Presbyterian Church USA) contains the order of the service for Transfiguration of the Lord. This order is either combined with the Sunday liturgy or replaces it in those congregations which orient themselves towards liturgical practices and observances. 
- Feast of the Ascension
- Ministry of Jesus
- Miracles of Jesus
- Transfiguration of Jesus in Christian art
- Festival icons for the Christian year by John Baggley 2000 ISBN 0-264-67487-1 pages 58-60
- Christian liturgy by Ignatius Puthiadam 2003 ISBN 81-7109-585-2 page 169
- Kitchin, Rev. William P. H., Ph.D. (April 1916). "Priests as Soldiers". The American Ecclesiastical Review; a monthly publication for the clergy (Philadelphia: The Dolphin Press) 54 (4): 431.
- Philip H. Pfatteicher New Book of Festivals and Commemorations: A Proposed Common Calendar of Saints 2008 p378
- "Epiphany". Evangelical Lutheran Church in America. Retrieved 19 August 2011.
- Quoted after "A Harmony of the Gospels, II" Edinburgh: St Andrew Press, 1972, p. 199.
- The Book of Common Worship, PCUSA. ISBN 0-664-22088-6 Westminster John Knox Press, Louisville, London, 1993, pages 214-220