Understanding the Lectionary Cycles (Years A, B, C and I, II)

Since the lectionary reform that followed the Second Vatican Council, the Church has read Scripture at Mass on fixed, repeating cycles, designed so that a Catholic who attends Sunday Mass hears the heart of the whole Bible every three years, and a daily Mass-goer hears substantially more. Knowing how the cycles work tells you which Gospel this year belongs to, why the weekday first reading changed books overnight, and when your favorite passage will come around again.

Sundays: the three-year cycle (A, B, C)

Sunday readings run on a three-year cycle, and each year is anchored to one synoptic Gospel:

• Year A: the Gospel of Matthew.
• Year B: the Gospel of Mark (with John 6, the Bread of Life discourse, filling Mark's short year in high summer).
• Year C: the Gospel of Luke.

John has no year of his own; his Gospel appears every year in the seasons where the Church has always read him: Lent, Easter, and the great feasts. On most Sundays the first reading is chosen to echo the Gospel, the psalm responds to the first reading, and the second reading works through the apostolic letters on its own semi-continuous track.

Weekdays: the two-year cycle (I and II)

Weekday Mass in Ordinary Time uses a two-year cycle for the first reading and psalm: Cycle I in odd-numbered years, Cycle II in even-numbered years. The weekday Gospel, though, is the same every year: Mark, then Matthew, then Luke, read nearly continuously across the year. This is why a daily homilist meets the same Gospel passage annually while the first reading beneath it alternates. In Advent, Christmas, Lent, and Easter the weekday readings are proper to the season and identical in both cycles.

When the cycle changes, and which year we are in

Both cycles turn over not on January 1 but on the First Sunday of Advent, the beginning of the liturgical year, in late November or early December. The rule of thumb for Sundays: take the calendar year in which most of the liturgical year falls and divide by three. A remainder of 1 means Year A, 2 means Year B, and 0 means Year C. So the liturgical year that runs from Advent 2025 through November 2026 is Year A, and Advent 2026 opens Year B.

Feasts, solemnities, and other exceptions

Solemnities and feasts bring their own proper readings that override the cycle: Christmas, Epiphany, the Assumption, All Saints, a parish's patronal feast. Some solemnities have their own miniature A/B/C rotation; others use the same readings every year. Ritual Masses (weddings, funerals, confirmations) have their own lectionary sections entirely, which is why wedding readings and funeral readings are chosen from approved lists rather than taken from the day.

Why this matters for preaching and prayer

For preachers, the cycles are an inheritance: everything you prepared for the 23rd Sunday of Year A is relevant again three years later, and a weekday Gospel homily is potentially reusable every year. For everyone else, the cycles are a curriculum: follow them for three years and the Church will have walked you through the better part of the New Testament and a generous sweep of the Old. To see how the parts of the Mass frame these readings, see the Order of the Mass, or read how to write a homily on what to do with them.