Paschal Full Moon: the curious and complicated link between Easter, Equinox and moon.

Original written on March 2021, updated April 2022

Easter is the most important feast day in the Christian calendar. Regularly observed from the earliest days of the Church, it celebrates Christ’s resurrection from the dead, following crucifixion. It marks the end of Holy Week, the end of Lent, and the last day of the Easter Triduum (starting from the evening of Maundy Thursday, through Good Friday, Holy Saturday, and Easter Sunday), as well as the beginning of the Easter season of the liturgical year.
The resurrection represents the triumph of good over evil, sin, death, and the physical body, and the reminder that death brings life.
Springtime is also a welcomed sign after the long days of winter with warmer weather and freshly sprung flowers. Unlike Christmas, which falls on the same date each year, Easter and the celebrations leading up to it change dates every year.
Easter is what’s known as a “movable feast” or, to be clear, a religious holiday that may fall on a different calendar date from year to year.
So you may find yourself wondering how the date of Easter is determined.

The date of Easter is tied to the full Moon, to the March equinox (also called the spring or vernal equinox), but also the relationship between them.
Thanks to this, determining when Easter will be can get more than a bit confusing.

Here’s the basic rule for finding the date:
Easter is observed on the Sunday following the so-called Paschal Full Moon, which is the first full Moon that occurs on or after the March equinox.
For example, if the equinox were to occur on March 21 and the full Moon were to occur three days later, on March 24, Easter would be observed on the first Sunday after March 24.
However, thanks to the motions of our Earth and the Moon herself, as well as the inelasticity of calendars, sometimes calculate Easter’s date can get more complicated.
In, 2021, for example, the March equinox occurred on Saturday, March 20, and the first full Moon to occur after that date is March’s full Worm Moon, last Sunday, on March 28.
This makes March’s full Moon the Paschal Full Moon as well. Therefore, Easter will be observed on the first Sunday after March 28, Sunday, April 4!
Just a little bit complicated, that’s true?
The biggest cause of confusion regarding Easter is the twisted web of dates that are used to determine the beloved holiday. And If you take the rule given above at face value, things don’t always work out quite right.
This is exactly what happened, for instance, in 2019, when the March equinox occurred on March 20 at 5:58 P.M., with the full Moon reaching its peak four hours later, at 9:43 P.M.
But wait, that means that the full Moon and the March equinox happened on the same date, which should have celebrated Easter on Sunday, March 24, right? Well, not quite, because the dates of the full Moon and the March equinox that are used to calculate Easter are not the astronomical dates of these events, but rather the ecclesiastical dates….
The astronomical dates of the full Moon and the March equinox are the actual, scientifically determined dates of these events. For example, the equinox occurs at the exact moment when the Sun crosses Earth’s equator, when day and night are approximately equal. Similarly, the full Moon occurs when the Moon reaches peak illumination by the Sun.
On the other hand, the ecclesiastical dates of the full Moon and the March equinox are those used by the Christian Church, and they were defined long ago in order to aid in the calculation of Easter’s date, which means that they may differ from the astronomical ones.
In A.D. 325, a full Moon calendar was created that did not take into account all the factors of lunar motion that we know about today and, interestingly, the Christian Church still follows this calendar.
This means that the date of the ecclesiastical full Moon may be one or two days off from the date of the astronomical full Moon.
Additionally, the astronomical date of the equinox changes over time, but the Church has fixed the event in their calendar to March 21, and this means that the ecclesiastical date of the equinox will always be March 21, even if the astronomical date is March 19 or 20.
Due to these rules, in 2019, the ecclesiastical full Moon occurred before the ecclesiastical Vernal Equinox, which meant that Easter would not be observed until after the next full Moon (the Paschal Full Moon) in mid-April. Thus, Easter was celebrated later, on April 21, 2019!
Fun Fact: the word “Paschal,” which is used in the ecclesiastical (Christian church) calendar, comes from “Pascha,” a transliteration of the Aramaic word meaning “Passover.”

But how late can Easter be?
Over a 500-year period (from 1600 to 2099 AD), it just so happens that Easter will have most often been celebrated on either March 31 or April 16.
For the western Christian churches and others that use the Gregorian calendar for their calculations, Easter can occur as early as March 22 and as late as April 25.
For the Eastern Orthodox churches and others that use the Julian calendar for their calculations, the observance can occur between April 4 and May 8 in the Gregorian calendar.
But also the full Moon nearest to Easter can change. Sometimes, it’s the full Moon that occurs in March and sometimes it’s the full Moon that occurs in April: in 2021, March’s full Moon on March 28 will be nearest to Easter, on April 4!

And when is the Paschal Full Moon in 2022?
Technically, the Paschal Full Moon occurs on the 14th day of the lunar month that occurs on or after March 21 according to ecclesiastical calculations using the Metonic cycle. But in many cases, it coincides with the astronomical full Moon on or after the actual March equinox. Using the astronomical dates for 2022, the vernal equinox in the Northern Hemisphere occurred on Sunday, March 20, and the first full Moon to occur after that equinox date was April’s full Pink Moon, which rises on Saturday, April 16.
According to the general guideline, this makes April’s full Moon the Paschal Full Moon and therefore Easter would be observed on the first Sunday after April 16: Sunday, April 17! For 2022, this Easter date agrees with official ecclesiastical calculations.

In any case, independently if you understood something or not, from all the Editors here at Random-Times, we wish you a Happy Easter and a joyous spring season!