With the first Sunday of Advent, a new liturgical year begins in the Catholic Church, with the readings corresponding to Cycle C of odd-numbered years. What does this liturgical practice entail?
The beginning and end of the liturgical year
The United States Conference of Catholic Bishops (USCCB) explains on its website that the liturgical year is made up of six times or seasons: Advent, Christmas, Lent, the paschal Triduum, Easter, and Ordinary Time.
The conference notes that the new 2025 liturgical calendar will begin with the first Sunday of Advent on Dec. 1, 2024, and will conclude on the Saturday after the solemnity of Our Lord Jesus Christ, King of the Universe, which will be Sunday, Nov. 23, 2025.
The three-year cycle
Perhaps less known is that the liturgical calendar has a three-year cycle, repeating every three years, which determines the biblical readings for Sunday Masses.
St. Paul VI in his apostolic constitution Missale Romanum states that “all the Sunday readings are divided into a three-year cycle” and the Ordo Lectionum Missae (“Order of Mass Readings,” 1969) explains that each liturgical year will be designated “with the letters A, B, C.”
The ordo of 1981 specifies that Cycle C is designated as all years “that are multiples of 3.” Thus the 2025 liturgical calendar uses Cycle C.
In Cycle A, the Sunday Gospel is generally taken from Matthew, in Cycle B from Mark, and in Cycle C from Luke, while the Gospel of John is read primarily at Easter.
During the Easter season, the first reading is from the Acts of the Apostles. But the second reading in Cycle A is mainly from the First Letter of St. Peter; in Cycle B, from the First Letter of St. John; and in Cycle C, from Revelation.
In Ordinary Time, the First Letter to the Corinthians is read in all three cycles, while the Letter to the Hebrews has been divided in two, with one part read in Cycle B and the other in Cycle C.
Why an odd year?
On weekdays, also called “ferias,” the readings of the Mass have a different order. Lent, Advent, Christmas, and Easter have their own texts, according to a Catholic News Agency report.
In Ordinary Time, the Gospels are determined by a cycle of readings that is repeated every year. However, the first readings, which are generally from the Old Testament and the apostolic letters, have a double cycle, made up of an even and an odd year.
The ordo of 1969 specifies that “Year I” is for “odd years” and “Year II” is for “even years.” Therefore, the 2025 liturgical calendar is Year I, or an odd year.
The purpose of the cycles with even and odd numbers
This whole distribution of the readings by cycles and even or odd years has its source in the Constitution on the Sacred Liturgy, Sacrosanctum Concilium, where the Second Vatican Council asks that the “treasures of the Bible” be opened more to the faithful during Mass.
“In this way a more representative portion of the holy Scriptures will be read to the people in the course of a prescribed number of years,” the document states.
Thus, after three cycles, one will have heard a large part of sacred Scripture, and if one goes to daily Mass for two years, he or she will have gone even further into the Bible.
