The Rules of Easter

It’s all about the Vernal Equinox

April 16, 2019

easter eggs.jpg

Photo from Pixabay

“The first Sunday following the full moon after the vernal equinox.”


You would think something this simple would be without controversy, but as history tells us, it is not.

For Christians throughout the word, Easter marks the day of resurrection. Since as early as 325 AD, with the first council of Nicea, however, the date on which Easter is celebrated has been disputed.

According to the Infallible Wikipedia:

“Easter and the holidays that are related to it are moveable feasts which do not fall on a fixed date in the Gregorian or Julian calendars which follow only the cycle of the sun; rather, its date is offset from the date of Passover and is therefore calculated based on a lunisolar calendar similar to the Hebrew calendar. The First Council of Nicaea (325) established two rules, independence of the Jewish calendar and worldwide uniformity, which were the only rules for Easter explicitly laid down by the council. No details for the computation were specified; these were worked out in practice, a process that took centuries and generated a number of controversies. It has come to be the first Sunday after the ecclesiastical full moon that occurs on or soonest after 21 March, but Pink-Moon-2018-1311105calculations vary.”

One might think that setting out a fairly straight forward calculation would end the debate but, over the centuries, it’s become more confusing.

Things really went sideways when, in 1582, Pope Gregory XIII decreed that the Julian calendar was way off and introduced his own calendar. The Gregorian calendar is the one we still use today.

So what does that have to do with Easter and how to calculate the date? There are people in the world who still – over 400 years later – like the Julian calendar and use it to determine the date Easter is celebrated.

There’s also the whole question of the equinox. Back in the fourth century there was no modern science used to calculate the exact moment of the equinox. Instead it was determined based on the above mentioned lunisolar calendar. Which is a fancy way of saying that the people who use such calendars needed a way to adjust the dates based on what was happening around them. Think of it as the spring equinox begins 14 days AFTER the new moon or, approximately, with the full moon of the season.

According to religious rules about Easter, then, the holiday is not truly based on it being on the first Sunday following the full moon after the vernal equinox. No, the calculation is based on it occurring on the first Sunday following the full moon AFTER March 21.

This year Easter falls on April 21. But should it? The full moon and the vernal equinox both occurred on March 20 – a mere 3 hours and 45 minutes apart- with the equinox crossing the finish line first at 2:58 pm (PDT).  The moon was full at 6:43 p.m. So by scientific calculation, Easter SHOULD have already happened on March 24.

Instead, the rule – for those who follow the Gregorian calendar – is to think of March 21 as the equinox which places Easter on this coming Sunday. In the Infallible Wikipedia article, there’s an interesting table which shows the calculated dates of Easter for each competing calendar.

Full Moon
Astronomical Easter


4 April

5 April

12 April


23 March

23 April

27 March

1 May


11 April

16 April


31 March

1 April

8 April


21 March

20 April

24 March

21 April

28 April


8 April

9 April

12 April

19 April


28 March

4 April

2 May


Note that they have a column for Astronomical Easter giving this year three different dates from which to choose. The chart is also incorrect as we know the scientific full moon occurred on March 20 and not the 21.

And for the record? The most common date for Easter to occur since the inception of the Gregorian calendar through the year 3000 is April 16.

One of these days I’m certain the whole controversy will be settled. In 1997 a movement was afoot to make a change. Also from the Infallible Wikipedia:

“At a summit in Aleppo, Syria, in 1997, the World Council of Churches (WCC) proposed a reform in the calculation of Easter which would have replaced the present divergent practices of calculating Easter with modern scientific knowledge taking into account actual astronomical instances of the spring equinox and full moon based on the meridian of Jerusalem, while also following the Council of Nicea position of Easter being on the Sunday following the full moon. The recommended World Council of Churches changes would have sidestepped the calendar issues and eliminated the difference in date between the Eastern and Western churches. The reform was proposed for implementation starting in 2001, but it was not ultimately adopted by any member body.”

And so it goes. All I know is that hunting for Easter Eggs is usually much more pleasant the third weekend of April than it is in late March. Plus, for our family, Easter this year coincides with my father’s 96th birthday! It will be the fourth time in his life that Easter is on the same day. The other years were 1935, 1946, and 1957.

The links!




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