This article provide some guidance that may help make sense of the rules that govern which Propers are said for the Masses at this time of the year in the traditional Latin calendar.
- First thing to remember is that the liturgical year begins on the First Sunday of Advent.
- The second thing is that the liturgical year ends on the Last Sunday after Pentecost.
Comparing the Time After Epiphany with the Time After PentecostTwo parts of the church year are variable. All the other parts of the church year have a fixed number of days that do not vary. The two variable parts of the Church year are:
- "Time after Epiphany"
- "Time after Pentecost"
The Time after Epiphany comes first, after Advent, Christmastide, and (of course) Epiphany. The Time after Pentecost comes after Septuagesima, Lent, Easter Time, and (of course) Pentecost.
The following pie chart is from the Roman Missal.
- “Time after Pentecost” is on the left in green, which is the liturgical color for the season; it has by far the biggest wedge, which has between 23 to 28 Sundays.
- "Time after Epiphany" is shown on the right, also in green, and it has a small wedge with between 1 and 6 Sundays.
These two times are reciprocally related. When the "Time after Epiphany" has more Sundays, the "Time after Pentecost" has fewer Sundays.
Variable Feasts Affecting the Numbers of SundaysThe number of Sundays after Pentecost and the number of Sundays after Epiphany both change every year because the dates of the First Sunday in Advent and of Easter Sunday are variable:
- The First Sunday of Advent occurs on the fourth Sunday before December 25. Because December 25 can occur on any day of the week, the date of the first Sunday of Advent can be any Sunday from November 27 to December 3.
- Easter is on the first Sunday after the first full moon after the Vernal (Spring) equinox (which is assigned to March 21). Most of us are aware that the date of Easter changes because it is based on a lunar calendar to correspond to the Jewish feast of Passover. As a result of the variability of the dates of the full moon, Easter can occur on any of 35 possible Sundays from March 22 to April 25th.
Effects of Variable Feasts on the Numbers of SundaysThe variable dates of Advent and of Easter occurring earlier or later in a year are what lengthen and shorten the Time after Epiphany and the Time after Pentecost:
- If the start date of Advent is early, the total number of Sundays after Epiphany may be increased and the total number of Sundays after Pentecost may be reduced
- If the start date of Advent is late, the total number of Sundays after Pentecost may be increased and the total number of Sundays after Epiphany may be reduced.
- If Easter comes early, Septuagesima must also start earlier, which may reduce the number of Sundays after Epiphany and increase the number of Sundays after Pentecost by the same number.
- If Easter comes later, more Sundays (up to the maximum of six) may occur during the Time after Epiphany, and a corresponding fewer number of Sundays may occur during the Time After Pentecost.
Rules for Masses at the End of the Time after Pentecost
With all of the above being noted, let's look at the rules for which Mass Propers are said at this time when we are approaching the end of the Church year.
On the last Sunday before Advent, the Mass for the 24th and Last Sunday after Pentecost is always said. This Mass uses the Introit, Gradual, Offertory, and Communion from the 23rd Sunday after Pentecost, but it has its own Collect, Epistle, and Gospel.
23rd Sunday after Pentecost:• If the 23rd Sunday is the Last Sunday before Advent, the Mass called the “Last Sunday after Pentecost” is said.
• Otherwise, the Mass called the “Twenty-Third Sunday after Pentecost” is said.
More Than 24 Sundays after Pentecost:When there are between 24 and 28 Sundays after Pentecost, things get a bit more complicated.
- The Introit, Gradual, Offertory, and Communion of the 23rd Sunday after Pentecost are repeated on all the Sundays between the 24th and 28th Sunday after Pentecost.
- The Collect, Epistle, and the Gospel are taken from the Masses that were omitted from the Sundays after Epiphany. (Remember that during a year when there are more than 24 Sundays after Pentecost, there are always a corresponding fewer number of Sundays after Epiphany.)
The following table shows which Masses should be used for the Collect, Epistle and the Gospel, Secret, and Postcommuniion, according to whether the Time after Pentecost has 24, 25, 26, 27, or 28 Sundays.
Table: Rules for What Propers to Use Between 23rd and 28th Sundays After PentecostHow to Use the TableFind the number of Sundays after Pentecost for the current year in the columns under "If the Number of Sundays after Pentecost is:". For example, if the number is 28, follow the column under 28 for what Mass to use for the Collects, Epistle, and Gospel on the 24th, 25th, 26th, 27th, and 28th Sundays, which are given in the right column.
 The Propers of the Mass change either according to the season or to the feast or event being celebrated on a particular day. They include the Introit, the Collect, the Epistle, the Gospel, the Offertory, the Communion, the Secret, and the Post-Communion.
 The Roman Missal (1962) notes that the Mass for “The First Sunday after Pentecost” has been replaced with the Mass for Trinity Sunday. The old Mass called “First Sunday after Pentecost” is still in the Missal, but it is “only celebrated during the following week on days where there are no feasts of Saints.” The Mass for Trinity Sunday counts as the First Sunday after Pentecost; the next Sunday is the Second Sunday after Pentecost, and so on.
 Adapted from the Roman Missal (1962)