Almost all moveable feasts can be calculated by offsetting a specific number of days from Easter, but there is one minor exception that relies on a different anchor point.
The Catholic Church categorises its moveable feasts into two main groups: the Paschal Cycle (which ties directly to Easter) and the Advent/Epiphany Cycle (which anchors to Christmas or the nearest Sunday to a specific fixed saint’s day).
Here is the breakdown of the major moveable feasts and exactly how to calculate them.
The Paschal Cycle (Calculated Directly from Easter)
The vast majority of moveable feasts can be precisely calculated using a mathematical offset (addition or subtraction of days) from Easter Sunday.
- Ash Wednesday: Easter minus 46 days
- Palm Sunday: Easter minus 7 days
- Good Friday: Easter minus 2 days
- Ascension Thursday: Easter plus 39 days (often moved to the following Sunday in many dioceses)
- Pentecost Sunday: Easter plus 49 days
- Trinity Sunday: Easter plus 56 days
- Corpus Christi: Easter plus 60 days (traditionally a Thursday, often moved to the following Sunday)
- Sacred Heart of Jesus: Easter plus 68 days (always the Friday after Corpus Christi)
The Epiphany and Ordinary Time Gap
The number of weeks of “Ordinary Time” observed before Lent is also entirely dependent on Easter. Once Ash Wednesday’s date is calculated, the Church simply counts backward to determine when the Baptism of the Lord (the end of the Christmas season) cuts off and Ordinary Time begins.
The Exception: Advent and Associated Feasts
The only true moveable feasts that cannot be calculated by offsetting Easter are those belonging to the Advent cycle. These are anchored to Christmas Day (December 25), which is an immovable solar feast.
- First Sunday of Advent: Calculated as the closest Sunday to the Feast of St. Andrew (November 30), whether before or after. It can also be found by counting back exactly four Sundays before December 25.
- Solemnity of Christ the King: In the modern Roman Calendar, this is celebrated on the final Sunday of the liturgical year. It is calculated as exactly one Sunday before the First Sunday of Advent.
- Holy Family: Celebrated on the Sunday between Christmas and New Year’s Day (or December 30 if Christmas falls on a Sunday).
If you are writing a script or a calendar algorithm, you only need two anchor dates to map out the entire Catholic liturgical year: the date of Easter (calculated via the lunar computus method) and the fixed solar date of Christmas.