Easter and the Paschal Full Moon

The Curious Link Between Easter, the Equinox, and the Moon

February 8, 2021
Spring Moon

Did you know that the date of Easter is tied to the full Moon and the March equinox? Let us explain this curious connection …

Easter and the Paschal Full Moon

Easter is what’s known as a “movable feast”—in other words, a religious holiday that may fall on a different calendar date from year to year.

The date of Easter is tied not only to the full Moon, but to the March equinox (also called the spring or vernal equinox) and the relationship between them, too. 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 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 two days later, on March 23, Easter would be observed on the first Sunday after March 23.

However, thanks to the motions of our planet and the Moon, as well as the inelasticity of calendars, calculating Easter’s date can get more complicated sometimes! Read on to learn more…

When Is the Paschal Full Moon in 2021?

This year, the March equinox occurs on Saturday, March 20. The first full Moon to occur after that date is March’s full Worm Moon, on Sunday, 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!

► See our Easter holiday page to learn more about Easter’s date, Easter traditions, recipes, and more.

Photo by jakkapan/Shutterstock

A Difference of Dates

The biggest cause of confusion regarding Easter is the tangled web of dates that are used to determine the holiday. If you take the rule given above at face value, things don’t always work out quite right.

This is exactly what happened in 2019. The March equinox occurred on March 20 at 5:58 P.M. EDT, with the full Moon reaching its peak four hours later, at 9:43 P.M. EDT. But wait—that means that the full Moon and the March equinox happened on the same date, which should have landed Easter on Sunday, March 24, right? Well, not quite.

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.
  • The ecclesiastical dates of the full Moon and the March equinox are those used by the Christian Church. 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 dates of these events.

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. The Christian Church still follows this calendar, which 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. 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 on Sunday, April 21, 2019. 

Fun Fact: “Paschal” stems from Pascha, the Greek and Latin word for Passover.

How Late Can Easter Be?

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. 

Learn more about how to calculate the date of Easter.

Which Full Moon is Nearest to Easter?

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 (March 28) will be nearest to Easter (April 4).

See more information about March’s full Pink Moon.

2021 Moon Wall Calendar

Want to enjoy the beautiful Moon year-round? Check out our Moon Calendar here!

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