While I traveled this past week, here is an excerpt from a book entitled What's the Smoke For?

 

Dear Johan, At Mass, people keep making references to Years A, B, and C. That all sounds like gibberish to me. What are they talking about? This must be another of those Catholic oddities.

Gentle Reader-I know it sounds a bit crazy. Dare I add to the confusion by mentioning that we also have Years I and II? Do not fear, though, it will all make sense soon. And no, it is not just a Catholic thing.
Sometimes people seem to think that the Lectionary was given to us by Jesus himself. Though of course the Bible contains the word of God, it did not come with instructions as to what ought to be proclaimed when. That, we had to discover over the course of our liturgical history. And discover, we did.
Borrowing from their own Jewish tradition, early Christians continued the custom of reading Scripture when they gathered. At first they must have read from the so-called Old Testament books and shared their memories of Jesus. Toward the end of the first century there are indications that readings from the New Testament, that is, the letters of the apostles, were also included. And as soon as the gospels were written and circulated they were read as well. The way this was done is, however, not entirely clear and undoubtedly differed from region to region. Lectio continua, the continued reading of one book after another, may have been the practice in most early Christian churches.
By the fourth century the liturgical seasons were roughly established and the feasts of martyrs and saints started to fill out the liturgical year. The different seasons and feasts required their own specific readings. Thus the older custom of lectio continua was gradually abandoned in favor of prescribed readings matching each specific day.
At first these selections of readings were communicated through simple lists. Eventually the lists were replaced with veritable books. Thus there was the Epistolarium or Epistolary, which contained readings from the letters of the New Testament and select readings from the Old Testament, and the Evangeliarium or Evangeliary, which contained the gospel readings. The book that contained both is known as a Lectionarium or Lectionary, literally meaning book of lessons or readings. Though these lectionaries at first varied from region to region, by the thirteenth century the same Lectionary was used throughout most of the Catholic Church. This Lectionary recurred year after year, so there were no Years A, B, and C or I and II as of yet. This did not happen until the Second Vatican Council.
One of the goals of this council was to increase the emphasis on the word of God, both within and outside of the liturgy. Up until then only about 1 percent of the Old Testament and about 16.5 percent of the New Testament were read during the Eucharist. This changed dramatically as now we read about 13.5 percent of the Old Testament and 71.5 percent of the New Testament.
In order to accommodate this, the Lectionary was expanded from one recurring year to three recurring years (A, B, C) for Sunday and two recurring years (I, II) for weekdays. Each of these years begins with the new liturgical year on the first Sunday or weekday of Advent.
Sundays and solemnities have four readings. The first reading is taken from the Old Testament, except during Easter when it is taken from the New Testament. The second reading, which is best sung, is taken from the Psalms. The third reading is taken from the New Testament. The fourth reading is taken from one of the gospels. In terms of the gospels, Matthew is predominant in Year A, Mark in Year B, and Luke in Year C. The Gospel of St. John is used throughout each one of the years when appropriate, mostly during the Easter season.
Weekdays have three readings. The first reading is selected either from the Old Testament or the New Testament, relative to the season. The second reading is one of the Psalms. The third reading is taken from one of the gospels. These are read semi-continuously starting with Mark, followed by Matthew and Luke. John is read during the Easter season. The gospel readings are the same in Years I and II.
Finally, as to your suggestion that this might be an oddity specific to Catholics, it is not. Please note that after the Reformation several Protestant denominations continued to use the Roman Catholic Missal, albeit with some changes. When the Catholic Church adapted the post–Vatican II Sunday Lectionary, it was quickly adopted and adapted by different Protestant denominations. So, they too have Years A, B, and C. As a result, on many occasions the readings we use in our Catholic churches are also used in other Christian churches.
 
© 2015 Order of Saint Benedict, Collegeville, Minnesota. Excerpted from What’s the Smoke For? And Other Burning Questions about the Liturgy by Johan van Parys © 2014 Order of Saint Benedict, published by Liturgical Press, www.litpress.org. Used by permission.

      Fr. Jerry Ragan