The Liturgical Year and the Civil Calendar

Published

May 2, 2024

Note

Many online sites explain the liturgical calendar that organizes the readings of the Revised Common Lectionary. This page summarizes the most important concepts underlying the calendrical functionality of the Lectionary.jl package.

Overview

The liturgical year is organized in two cycles. One is anchored by the fixed date of Christmas on December 25; the second is anchored by the movable date of Easter. Each cycle has three liturgical seasons: a preparatory season, a celebratory season, and “ordinary time.”

The Christmas cycle

The seasons of the Christmas cycle are Advent, Christmastide, and ordinary time after Epiphany. Advent begins four Sundays before Christmas Day (so in the range of November 27 to December 3, depending on what day of the week Christmas Day falls on). Christmastide is the “twelve days of Christmas” that run from Christmas Day through Epiphany (January 6). The third season, ordinary time after Epiphany, runs until Lent begins on Ash Wednesday.

The Easter cycle

The seasons of the Easter cycle are Lent, Eastertide, and ordinary time after Pentecost. Lent begins on Ash Wednesday, 46 days before Easter. Ash Wednesday can fall anytime from February 4 to March 10. Eastertide runs from Easter through Pentecost. Easter Day occurs between March 22 and April 25; Pentecost is the Sunday 49 days after Easter. Ordinary time after Pentecost fills the rest of the liturgical until the beginning of Advent for the following year.

Determining the date of Easter

In the RCL calendar, Easter is the Sunday following the first full moon that falls on or after the spring equinox, but instead of the astronomical equinox, the liturgical year uses the fixed calendar date of March 21. The date of Easter can therefore range from March 22 at the earliest to April 25 at the latest.

Range of possible dates for the beginning of each liturgical season

  1. First Sunday of Advent: November 27 - December 3
  2. Christmas Day: December 25
  3. Epiphany: January 6 (ordinary time begins the following day)
  4. Ash Wednesday: February 4 - March 10
  5. Easter Day: March 22 - April 25
  6. Pentecost: May 10 - June 13 (ordinary time begins the following day)