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Why Easter "Hops" Around the Calendar

Happy Easter! Yes, we are still celebrating the season of Easter, which last for fifty days until Pentecost.

I happened to be looking up the date for Easter next year (which is April 21) and was curious about how the date for Easter is decided and why it hops around so much. (This year Easter was on April 1; last year it was April 16; the year before it was March 27.) I learned that not only is there a very specific, and somewhat complicated, way to determine the date of Easter, but that this process has a rich history and even has its own name: computus, which is Latin for “computation.” According to this calculation, Easter falls on the first Sunday following the full moon that follows the vernal (Spring) equinox.

(Image: The astronomical clock inside Notre-Dame de Strasbourg)

Today we pretty much take the creation of calendars for granted. The correct date always appears on our phones or computers, and we can google the date of Easter years in to the future if we like. However, for hundreds of centuries, the creation and use of calendars was a complex mathematical, astronomical, and theological practice.

The Computus was decided in the year 325 CE by the Council of Nicaea, the first ecumenical council of the Christian church. Prior to this point, churches would celebrate Easter on different dates—some celebrating Easter on the first day of Passover and some on the following Sunday.

The Gospels of Matthew, Mark, and Luke, describe the Last Supper (which we now observe as Maundy Thursday) as occurring on the first day of Passover, while the Gospel of John says that Passover was on Good Friday. There is a fair amount of theological discussion on this, but the point is that the resurrection most likely occurred sometime during Passover. Consequently, many early Christians celebrated Easter according to the date of Passover, which begins on the 15th day of the month of Nisan in the Hebrew calendar (a lunisolar calendar, meaning it is based on both the sun and the moon) and usually lasts seven or eight days.

(The Last Supper (Restored), Leonardo Da Vinci, 1945-1948)

The most widely used calendar across the world today is the Gregorian calendar, which is a solar calendar. The Gregorian calendar was adopted in 1582 by Pope Gregory XIII as a refinement of the previous Julian calendar, in part to correct the date of Easter. The Julian calendar, also a solar calendar, miscalculated the length of the solar year (which is why now have leap days). So, over time, the calculated date of Easter grew gradually earlier and earlier, until it was no longer being celebrated during the spring.

Because the calendar we use is a solar calendar and the date of Easter is based on lunar and solar calculations, the date of Easter moves every year. According to the Gregorian calendar, which uses March 21 as a fixed date for the vernal equinox, the earliest possible date for Easter is March 22 (this occurred in 1818 and will occur again in 2285), and the latest possible date is April 25 (this occurred in 1943 and will next occur in 2038). The graph below shows the distribution of possible dates for Easter:

The date of Easter is important not only because Easter is the most important celebration in the Christian church, but also because it is used to determine other important liturgical dates and seasons throughout the year. In the liturgical calendar, three seasons are determined by the date of Easter: Lent, Easter, and Pentecost, and three seasons are calculated based on the date of Christmas: Advent, Christmas, and Epiphany.

Christmas Cycle: *Advent: begins the fourth Sunday before Christmas *Christmas: December 25 *Epiphany: January 6, 13 days after Christmas

Easter Cycle: *Lent: 40 days (not counting Sundays) before Easter

*Easter: the first Sunday following the full moon that follows the vernal equinox

*Pentecost: the seventh Sunday (49 days) after Easter

*Ordinary Time/ the season after Pentecost: between Pentecost and Advent

The date of Easter and thus the liturgical calendar are important aspects of the Christian tradition. The church year, with its seasons of anticipation and celebration, of repentance and renewal, not only helps us relive the story of Jesus and his first followers but also helps us attend to the seasons of our own lives, with our own ups and downs, joys and sorrows, periods of activity and times of quiet. Easter is an especially important season for us as Christians; we are described as “an Easter people.” Easter is regarded as “the Queen of Feasts,” and each Sunday is “a little Easter,” which is why Sundays do not count in the 40 penitential days of Lent. So, Happy Easter, everyone! Happy Easter season, Easter people! [if !supportLineBreakNewLine] [endif]Grace and peace,


A member of St. Brendan's since 2014, I enjoy being a part of this welcoming and giving community of faith. However, I am not a theologian, biblical scholar, or official spokesperson for The Episcopal Church. If you read anything on this blog that is inaccurate or contrary to the teachings of The Episcopal Church, please consider it my error and let me know! If you have any questions, comments, or ideas for future blog posts, please email me at

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