Christmas is on December 25 every year. Halloween is every October 31 and Independence Day is on July 4th. Those are rock solid dates and it doesn’t matter what day of the week they occur. They don’t have to be on a Saturday, for example, although in every case that would be nice. Instead their significance is attached to the date itself.
But Easter is different. In has to be on a Sunday, and in 2021, Easter was on April 4. In 2022 it was on April 17. In 2023 it will be on April 9, and in 2024 it will be on March 31.
Kind of fascinating, isn’t it? It shifts every year, but it has to be more than just because Sunday is the day that Christ was resurrected (Matthew 28:1). From year to year the dates of Easter are weeks apart. Why not just choose the last Sunday of March, kind of like how we choose the last Thursday of November to celebrate Thanksgiving?
The problem comes from trying to keep the celebration of Christ’s resurrection closely aligned with the Hebrew calendar. As you may know, Christ was crucified on the Jewish convocation called Passover, and then three days later he resurrected. Passover is a Jewish holy day that commemorates when God freed the Hebrews from Egyptian slavery.
According to Exodus 12, the Hebrews were to sacrifice an unblemished lamb (sheep or goat) at twilight on the 14th day of the month of Abib (March/April). They were then to brush the blood onto the lintel and doorposts so that, “The blood shall be a sign for you on the houses where you are. And when I see the blood, I will pass over you; and the plague shall not be on you to destroy you when I strike the land of Egypt” (Exodus 12:13).
The Passover was to be consistently celebrated on the 14th day of the month of Abib: “Observe the month of Abib, and keep the Passover to the LORD your God, for in the month of Abib the LORD your God brought you out of Egypt by night” (Deuteronomy 16:1). Therefore, since Jesus became the fulfillment of the Passover lamb (John 1:29; Matthew 26:2), Christianity has chosen to stay as close to the biblical model as possible.
Now the fun part begins: we need to know when the month of Abib begins so we can count to fourteen days later, and that changes every year on our calendar, but not on the Jewish calendar
The first day of a month for the Hebrews was the first visibility of the new moon. The new moon is the sliver of a moon we see in the sky just as the sun sets. The Essenes, a first century Jewish sect, called it the Fingernail of God.
As you may know, the moon is invisible for 2-3 days every month because it is nearly in line with the sun (when it is perfectly in line we have a solar eclipse). It is therefore washed out by the sunlight for a few days until it reappears in the western sky at twilight because it is once again far enough away from the sun to be seen.
That is counted as the first day of the month, called first visibility, and it had to be attested to before the Sanhedrin by at least two witnesses. After it was confirmed, someone would blow the shofar (a trumpet made of a ram’s horn) which officially announced the month had begun.
This is why the Passover–the day of Christ’s crucifixion–changes every year: It must be fourteen days after the new moon of Abib, and we use a solar calendar not a lunar calendar. On the Jewish calendar Passover is the exact same date every year. The Hebrew calendar (and almost every other ancient calendar) paid attention to the cycles of the moon especially in regards to their religious festivals. Since a month (first visibility to first visibility) is either 29 or 30 days long, 12 lunar months only totals about 354 days. That’s ten days shorter than a solar year which is about 365.25 days. In practical terms, if a society didn’t recalibrate their religious lunar calendar with the cycles of the sun, then their spring festivals would eventually be celebrated in the summer, and then the fall, etc.
How the Hebrews recalibrated their calendar at the time of Christ was to add an extra month every 2 or 3 years which would realign the correct months with the correct seasons. It wasn’t a perfect system but it did the job and it was based on a combination of observation and calculation.
So here’s the nitty gritty:
Here’s an example of the new moon on Abib 1 (Nisan 1) in the year 2023 (which is on our March 22/23).
The green line swooping off to the left marks the path of the sun, moon, and planets called the ecliptic, and the other green line marks the meridian. When the sun is directly on the cross hairs, that is the spring equinox (which was two days earlier on March 20th).
The next picture shows the full moon 14 days later: Abib 14. I took out the horizon so it would be easier to see how the sun and moon are opposite of each other. It is a full moon.
The next series of pictures show how the same Hebrew dates (Abib 1 & 14) will look in 2024.
Abib 1:
Notice that the day the new moon occurs is now several days before the spring equinox.
Now let’s look at Abib 14 of 2024:
As you can see, the relationship of the sun and moon with the Ecliptic Meridian is slightly shifted from where it was a year earlier. This is why the solar calendar gives us a different date than the lunar calendar, and if this drift isn’t accounted for then the date of Passover would get further and further away from the spring equinox and the time of year when God commanded Passover to be celebrated. Since Christianity decided to celebrate the resurrection every year on a Sunday, they chose to put it on the first Sunday after the biblical date for Passover.
This is why the date of Easter changes every year.
Blessings.
