The Rules Behind the Calculation

How to determine any date on the Church Calendar

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How does this page work?

Using Christmas Day and Easter, for the year you select, it calculates the Seasons each time.

What are the Basic Rules for Calculating a Church calendar?

The Church Calendar has two fixed points: the Nativity of the Lord (Christmas), always on the 25th of December, and Easter, the first Sunday after the first full moon occurring on or after the spring equinox (the date (twice each year) at which the sun crosses the celestial equator, when day and night are of equal length). Modern programming languages now have a function called easter-date(). It will find the date of Easter in any year in the parentheses. This program uses these two dates (Christmas and Easter) to determine everything else.

  How is Advent Determined (Calculated) and When does it start?

Advent always has 4 Sundays, but it can be either 3 or 4 weeks. When Advent 4 is on Dec 24th, the morning is Advent 4, and then the afternoon is Christmas Eve. The Advent Sundays are calculated by finding the four Sundays before Dec 25^th, even if one of those Sundays is Christmas Eve. There can be up to two Sundays after Christmas, but most years, there is only one.

  How is Epiphany date determined? (What are The 12 days of Christmas?)

This is the twelve days of Christmas. Twelve days after Christmas (Dec 25) is Epiphany (Jan 6). The twelve days of Christmas is the time between Christmas Day (1st day of Christmas) and Epiphany (12th day of Christmas). It marks the time between the birth of Jesus Christ and the coming of the three wise men. The Sunday nearest to Jan 6 can be celebrated as Epiphany Sunday, or the first Sunday after Epiphany (The Baptism of the Lord). Epiphany Sundays are then counted until the Sunday before Ash Wednesday. The reading labeled the Last week of Epiphany is always last. So, if you have five weeks of Epiphany, instead of celebrating the fifth week, you celebrate the Last Sunday. An excellent way to remember is that the Last Sunday of Epiphany has the Ash Wednesday readings.

  How is the date of Lent determined?

Lent always has 46 days, 40 not counting the Sundays (which are a Feast day in Lent). It is always calculated back from Easter. Like Advent and the Easter Season, Lent has a fixed number of Sundays, and other seasons expand and contract to fit them.

  How is the date of Easter determined?

In 325CE, the Council of Nicaea established that Easter would be held on the first Sunday after the first full moon occurring on or after the spring equinox. From that point forward, the Easter date depended on the ecclesiastical approximation of March 21 for the equinox. Easter is delayed by one week if the full moon is on Sunday. Easter can be as early March 21^st as in the year 1818 or as late as May 10 in the year 2268.

Easter Determines these dates
Ash Wednesday (47 days before Easter)
Ascension Day (10 days before Whit Sunday)
Palm Sunday (1 week before Easter Sunday)
Pentecost (Whit Sunday) (7 weeks after Easter Sunday)
The Easter Season always has seven Sundays, plus Pentecost.

  When is Pentecost and how is that date determined?

Ends the fifty-day season of Easter (that’s what the Greek word “Pentecost” means!) It does not begin a “Pentecost Season."

  When is Trinity Sunday and how is that date determined?

Is the first Sunday after Pentecost.

  When is Ordinary Time? and Why is it called Ordinary?

Ordinary time (AKA Kingdomtide) does not mean common. It refers to Ordinal time, or Ordinal numbers. First, Second, Third, etc., are ranks, versus Cardinal numbers (1, 2, 3, etc.) which mean how many. Ordinary weeks are set backward from the last week of the Church Year, which is always Proper 29. When do the Proper’s start? It has been determined that the earliest possible Day of Pentecost, May 10, hence Proper 1, is “closest to May 11.” The Proper’s are planned backward. The Sunday before Advent 1 (of the following year) is Proper 29. Then the Proper’s fill in before that until they hit Pentecost, and the Proper closet to that Sunday after Pentecost is used. The early Proper’s are rarely used, but those reading still find their way in the lectionary because they are repeats of the last weeks of Epiphany. You may notice the readings for Proper 1 are just the same as the readings for the 6^th Sunday after Epiphany; Proper 2 is the same as the seventh Sunday after Epiphany. This continues to the 8th Sunday after Epiphany, the greatest number of Sundays possible after Epiphany..

Sixth Sunday after Epiphany	= Proper 1
Seventh Sunday after Epiphany	= Proper 2
Eighth Sunday after Epiphany	= Proper 3

Closest To

Any Sundays closest to a date are calculated like this

Sunday < Monday <Tuesday <Wednesday
Thursday> Friday> Saturday > Sunday

How are the Lectionary Cycles Calculation determined?

The Sunday Lectionary Cycle (Year A, B, or C) and Daily Office Cycle (One or Two) are simple. Daily Office One years start in even years (Advent 1 Sunday), and Daily Office Years start in odd years. The Sunday Lectionary Cycle starts incrementing 1968 by three years, and any Advent Sunday 1 that matches one of those years is Year A, same for Year B (1969) and Year C (1970).