The Paschal Triduum, often called the Easter Triduum or simply the Triduum, begins during Holy Week, and consists of Holy Thursday, Good Friday, Holy Saturday
(begins with the evening Mass of the Lord’s Supper on Holy Thursday, reaches its high point in the Easter Vigil, and closes with Evening Prayer on Easter Sunday)
which also includes the Great Easter Vigil, the high point of the Triduum . The word Triduum comes from the Latin word meaning "three days", consisting of three full days which begin and end in the evening.
1st Day: Considered the Christian Passover, this day is from Holy Thursday sunset until Good Friday sunset. On Thursday we celebrate The Evening Mass of the Lord's Supper and on Friday we celebrate the Lord's Passion.
2nd Day: Considered the Paschal Sabbath, this day is from Good Friday sunset until Holy Saturday sunset. In burial, the Lord rested, and we rest in him ("the day of rest" - even from liturgy).
begins on Holy Saturday sunset and ends with the Easter Vigil. On this day we reach the climactic point in the Easter Vigil and concludes with the Evening Prayer of Easter Sunday.
With the renewal of the Triduum:
- Lent is observed until the Mass of the Lord's Supper.
- The Great Three Days are celebrated.
- The Great Feast (Easter) is sustained for 50 days. Easter Sunday is both the final hours of the Triduum and the first hours of The Great Fifty Days.
The Triduum technically is not part of Lent (at least liturgically), but Holy Thursday, Good Friday, and Holy Saturday are still taken into account as part of the traditional forty day Lenten fast. The Triduum celebrates the heart of our faith, salvation, and redemption: the death and resurrection of Jesus Christ. Thus, the Triduum commemorates the Institution of the Eucharist (the "sacrament of sacraments"), the passion, crucifixion, death of the Lord, his descent to the dead, and finally his glorious resurrection on Easter Sunday morning. Along with the Ascension, these important events make up the Paschal Mystery.
Even though the liturgical year begins chronologically at Advent, it reaches its climax during the Easter Triduum, particularly at Easter, the "solemnity of solemnities," the "Great Feast." The Catholic Catechism describes the importance of the Triduum:
Beginning with the Easter Triduum as its source of light, the new age of the Resurrection fills the whole liturgical year with its brilliance. Gradually, on either side of this source, the year is transfigured by the liturgy. It really is a "year of the Lord's favor." The economy of salvation is at work within the framework of time, but since its fulfillment in the Passover of Jesus and the outpouring of the Holy Spirit, the culmination of history is anticipated "as a foretaste," and the kingdom of God enters into our time (1168).