Could you explain, briefly, how the cycle of readings for the Mass are determined?
Here’s a reply from Father Reginald Martin:
The Church embraced a new Lectionary in 2002. The principle by which it was organized was to give God’s people “a knowledge of the whole of God’s word.” The editors accomplished this task by presenting a cycle of readings for weekday Masses, which extends over two years, and another cycle for Sundays, which extends over three. The Sunday cycles devote one year to each synoptic writer — Matthew, Mark and Luke. We hear John’s Gospel every year during the Easter season.
Sunday Masses present three readings. During Ordinary Time, the second (New Testament) reading and Gospel are generally continuous week to week, but do not necessarily reflect one another. However, the first (Old Testament) reading reflects the Gospel theme. During Advent and Lent, the three readings reflect one another. During the Easter season, the first reading (from the Acts of the Apostles) is continuous.
Weekday Masses offer two readings. Each year traces Christ’s life through continuous readings of the synoptic Gospel accounts. The first readings, from the Old Testament, New Testament letters or Revelation, are continuous readings, spread over two years. Over three years, God’s people will encounter every book in the Bible except Judith.