Easter Triduum, Holy Triduum, Paschal Triduum, or The Three Days, is the period of three days that begins with the liturgy on the evening of Maundy Thursday (the vigil of Good Friday) and ends with evening prayer on Easter Sunday, the three-day period therefore from the evening of Maundy Thursday (excluding most of Thursday) to the evening of Resurrection Sunday. It recalls the passion, death, burial, and resurrection of Jesus, as portrayed in the canonical Gospels.
Since the 1955 reform by Pope Pius XII, the Easter Triduum, including as it does Easter Sunday, has been more clearly distinguished as a separate liturgical period. Previously, all these celebrations were advanced by more than twelve hours. The Mass of the Lord's Supper and the Easter Vigil were celebrated in the morning of Thursday and Saturday respectively, and Holy Week and Lent were seen as ending only on the approach of Easter Sunday.
After the Gloria in Excelsis Deo at the Mass of the Lord's Supper all church bells are silenced and the organ is not used. The period that lasted from Thursday morning to before Easter Sunday began was once, in Anglo-Saxon times, referred to as "the still days".
In the Catholic Church, weddings, which were once prohibited throughout the entire season of Lent and during certain other periods as well, are prohibited during the Triduum. Lutherans still discourage weddings during the entirety of Holy Week and the Triduum.
Maundy Thursday (also called Holy Thursday) 
- In some Protestant denominations, the Triduum begins with an evening worship service on Maundy Thursday.
- In the Catholic Church, in the Mass of the Lord's Supper, during the Gloria in Excelsis Deo, all church bells may be rung and the organ played; afterwards, bells and organ are silenced until the Gloria of the Easter Vigil.
- After the homily of the Mass a ritual washing of the feet is envisaged.
- The Mass concludes with a procession of the Blessed Sacrament to the altar of repose.
- Eucharistic adoration is encouraged after this, but if continued after midnight should be done without outward solemnity.
- The liturgical colour for the Mass vestments and other ornaments is white in the Catholic Church. In the Lutheran Church, the liturgical colour for Maundy Thursday is white or scarlet. In the Reformed tradition, white or gold may be used.
- In the form of the Roman Rite in use before 1955, there was no washing of the feet, which could instead be done in a separate later ceremony, and the Mass concluded with a ritual stripping of all altars, except the altar of repose, but leaving the cross and candlesticks. In the present form as revised in 1955, the altar is stripped bare without ceremony later.
Good Friday 
- On Good Friday, Christians recall the passion and crucifixion of Jesus.
- In the Roman Catholic, Lutheran, and Anglo-Catholic rites, a cross or crucifix (not necessarily the one that stands on or near the altar on other days of the year) is ceremonially unveiled. (In pre-1955 services, other crucifixes were to be unveiled, without ceremony, after the Good Friday service.)
- In the Catholic ritual, clergy traditionally begin the service prostrate in front of the altar. Mass is not celebrated on Good Friday and the communion distributed at the Celebration of the Lord's Passion is consecrated on Holy Thursday, hence the pre-1955 name "Mass of the Presanctified". In Anglican/Episcopal churches, there is no prayer of consecration on Good Friday, and the Reserved Sacrament is distributed at services on that day.
- Also in Catholicism, images of saints may, in accordance with local custom, be veiled throughout the last two weeks of Lent. Votive lights before these images are not lit. Crucifixes that are movable are hidden, while those that are not movable are veiled until after the Good Friday service.
- Catholic faithful typically venerate the crucifix by kissing the feet of the corpus. Veneration of a simple wooden cross is common in Anglican/Episcopal worship, with the faithful touching and or kissing it.
- Colors of vestments (and hangings, if kept) vary: no color, red, or black are used in different traditions. The Catholic Church uses red vestments, symbolic of the blood of Jesus Christ, but in the pre-1970 form of the Roman Missal the priest wears black, changing to violet for the communion part of the service. In Anglican/Episcopal services, black vestments are sometimes used. In The United Methodist Church, black is the liturgical colour used on Good Friday.
Holy Saturday 
- Holy Saturday is a commemoration of the day that Jesus lay in his tomb.
- In the Catholic Church, daytime Masses are never offered. In Anglican/Episcopal worship, there is no prayer of consecration or distribution of Reserved Sacrament on Holy Saturday, but a simple service of scripture readings and prayers may be held.
- Known as Black Saturday in the Philippines.
Easter Sunday 
- A vigil service is held after nightfall on Holy Saturday, or before dawn on Easter Sunday, in celebration of the resurrection of Jesus. Many of the details that follow hold for Anglican/Episcopal as well as Catholic worship.
- The ceremony of darkness and light is held at the beginning of the Vigil Mass.
- The paschal candle, representing Jesus' resurrection as the "return of light into the world," is lit from the new Easter fire.
- The solemn procession to the altar with the Paschal candle is formed.
- Once everyone has processed in, the Exsultet is intoned.
- After the Exsultet, everyone is seated and listens to seven readings from the Old Testament and seven Psalms. At least three of these readings and associated psalms must be read, which must include the account of the first Passover from the Book of Exodus. Pastoral conditions are taken into account when deciding on the number of readings. These readings account salvation history, beginning with Creation. In Anglican/Episcopal worship, there are nine possible readings from the Old Testament, and a minimum of two must be read, which must include the account of Israel's deliverance at the Red Sea.
- In Catholic practice, during the Gloria at the Mass, the organ and church bells are used in the liturgy for the first time in two days.
- If the lights of the Church have been previously left off, they are turned on as the Gloria begins.
- The Paschal candle is used to bless the baptismal font to be used in the celebration of the sacrament.
- The Great Alleluia is sung before the Gospel is read, Alleluia being used for the first time since before Lent.
- People receiving full initiation in the Church, who have completed their training, are given the Sacraments of Christian initiation (Baptism, confirmation, and the Holy Eucharist). In Catholic and Anglican/Episcopal tradition, the Easter Vigil is an especially appropriate day for Holy Baptism.
- In current practice, the use of lighting to signify the emergence from sin and the resurrection of Jesus varies, from the use of candles held by parishioners as well as candelabras lit throughout the church.
- If statues and images have been veiled during the last two weeks of Lent, they are unveiled, without ceremony, before the Easter Vigil service begins. (In the 1962 Catholic missal and earlier missals, they are unveiled during the "Gloria in Excelsis" of the Easter Vigil Mass.)
- Color of vestments and hangings: white, often together with gold, with yellow and white flowers often in use in many parishes.
- Easter Masses are held throughout the day and are similar in content to the Easter Vigil Mass.
- The date of Easter varies from year to year. It occurs on the first Sunday after the first full moon on or after 21 March, a date taken, in accordance with an ancient ecclesiastical tradition, to be that of the spring equinox, but which does not always correspond to the astronomical equinox. The Julian Calendar is taken as the basis of the calculations by nearly all Oriental Orthodox and Eastern Orthodox Churches and is accepted even by Latin Rite Catholics in countries such as Ethiopia and Greece. In the 20th and 21st centuries, the Julian Calendar's 21 March corresponds to 3 April in the Gregorian Calendar, the calendar used for civil purposes in most countries. The earliest possible date for Easter is 22 March, and the latest 25 April. These dates in the Julian Calendar now correspond to the Gregorian Calendar's 4 April and 8 May.
- During the Easter octave (and also during Holy Week) no other feast is celebrated. If Easter is very early, the solemnity of the Annunciation (25 March) may fall within the octave or Holy Week and is then transferred to the Monday after the octave.
- The Sundays of Advent, Lent, and Easter have precedence over all feasts and solemnities, solemnities being then transferred to the following Monday, unless they occur on Palm Sunday or on Sunday of the Lord's Resurrection. "The Solemnity of Saint Joseph, where it is observed as a Holyday of Obligation, should it fall on Palm Sunday of the Lord's Passion, is anticipated on the preceding Saturday, 18 March. Where, on the other hand, it is not observed as a Holyday of Obligation, it may be transferred by the Conference of Bishops to another day outside Lent."
- The solemnity of the Ascension is on the fortieth day of Easter, which is always a Thursday, although it may be observed on the following Sunday. Pentecost (or Whitsun) is the fiftieth day.
- The Easter season extends from the Easter Vigil through Pentecost Sunday on the Roman Catholic, Anglo-Catholic and Protestant calendars. In the pre-1970 Roman Catholic calendar the octave of Pentecost is included in Eastertide, which thus ends at None of the following Ember Saturday.
- During the 50-day Easter period, vestments are generally white or gold, but red when celebrating apostles and martyrs and on the solemnity of Pentecost. In the pre-1970 Roman Catholic calendar, with its 56-day Eastertide, red was used during the octave of Pentecost.
See also 
- "The Three Days: Maundy Thursday, Good Friday, and the Vigil of Easter". Evangelical Lutheran Church in America. 2012. Retrieved 1 April 2012.
- General Norms for the Liturgical Year and the Calendar, 19
- Catholic Liturgy, Holy Thursday Evening Mass of the Lord's Supper
- "The Paschal Triduum". American Bible Society. Retrieved 26 May 2011.
- "Holy Week". Catholic Encyclopedia. New York: Robert Appleton Company. 1913.
- "Banns of Marriage". Catholic Encyclopedia. New York: Robert Appleton Company. 1913.
- Rev. Thomas L. Weitzel. "The Triduum: Maundy Thursday with Footwashing". Evangelical Lutheran Church in America. Retrieved 1 April 2012. "The Maundy Thursday service is one of endings and beginnings. What was begun on Ash Wednesday is brought to a close here today. What begins today does not end until the resurrection of Easter. It is the ancient Triduum, "The Three Sacred Days," which lead us to Easter: Maundy Thursday, Good Friday, and Holy Saturday."
- General Instruction of the Roman Missal, 346
- "What is the meaning and use of liturgical colors?". Evangelical Lutheran Church in America. Retrieved 1 April 2012. "Maundy Thursday: For this fourth day of Holy Week, celebrated as the institution of the Lord’s Supper, scarlet or white is used."
- "Liturgical Colors and the seasons of the church year". United Church of Christ. Retrieved 1 April 2012. "On Maundy Thursday, White or Gold symbolizes the church's rejoicing in the sacrament of the Lord's Supper. But at the end of the Maundy Thursday celebration, the mood changes abruptly: all decorations are removed and the Holy Table is stripped bare. The church becomes as empty as a tomb. On Good Friday, either Black or Red is customary—although the use of no color at all is also appropriate."
- "Good Friday". Catholic Encyclopedia. New York: Robert Appleton Company. 1913.
- Covering of Crosses and Images in Lent
- Christian Advocate, Volume 5. The United Methodist Church. 1961. Retrieved 1 April 2012. "The liturgical color for the Lenten season is violet or purple, except for Good Friday when black is used."
- Catholic Culture accessed 12 August 2010
- United States Conference of Catholic Bishops. Accessed 12 August 2010
- Catholic Liturgy, Easter Sunday of the Lord's Resurrection, The Easter Vigil. Accessed 12 August 2010
- Catholic City Tenbrae Retrieved on April 5, 2007
- Universal Norms on the Calendar, 60. This is an exception to the normal rule that impeded solemnities are transferred to the closest day not ranked as feast or higher.
- Universal Norms on the Calendar, 5
- Universal Norms on the Calendar, 56