Why is Easter on different dates?

Why is Easter on different dates every year?

I remember wondering about this question every year as a child.  Christmas was on December 25th.  New Year's Day was January 1st.  Independence Day was July 4th.  Those were easy.

Other holidays were tougher but made sense once you figured it out.  Thanksgiving is the 4th Thursday in November.  Memorial Day is the 4th Monday in May.  Labor Day is the 1st Monday in September.  They were easy to understand once you knew how it worked.

This wasn't true with Easter.  As I got older I learned that Easter is the Sunday following the first full moon after spring solstice.  This means Easter can be celebrated anywhere from March 22 to April 25, a variation of 35 days.

Spring solstice is always on March 21st.  The moon takes 29.5 days to do a complete orbit around the earth.  A week is 7 days.  The 29-day moon cycle plus a maximum of a 6-day delay is why there's a variation in the holiday of 35 days.

To figure out the date of Easter, all you need is a lunar calendar.  In 2019, a full moon occurred on March 21st but the Christian rules state it has to be the first full moon after March 21st.  The next full moon happened on April 19th.  The following Sunday is April 21st and that is the date western churches celebrated Easter in 2019.

Isn't that easy?  OK.  Maybe not exactly easy but it is understandable once you know how it works.

A better question might be to ask is - why is it so complex?  Answering that question isn't so easy.

Why did the ancient church come up with such a weird method for determining a holiday?

Passover

Blame the Jews.  Now before you accuse me of being an anti-semite, this one really is at least partially their fault along with equal shares by the Babylonians and the Romans.

The book of Mark relates to us that six days before his resurrection Jesus was hailed by the crowds who had come to Jerusalem to celebrate the annual Passover feast.  So we know the resurrection occurred near the Jewish holiday of Passover.  This causes all sorts of problems when trying to come up with a date for Easter.

The reason for this is the Jewish calendar is a lunar calendar and most westerners have no experience with this type of calendar.


How did the Jews come up with their calendar?

The tower of Babel

Imagine you are a Babylonian living 3,000 years ago.  Calendars don't exist as we know them today but you are part of a greater society that stretches from Persia to Egypt and north to Greece.  As these societies expanded and commerce boomed it is clear they needed something else to help coordinate activity over long distances.  They needed a calendar.

So how do you come up with a calendar?  It may seem easy in hindsight but it's really not.  For the Babylonians, the answer was in the heavens. 

People today don't look at the moon as they did in ancient times but the moon can tell you many things.  Remember these people didn't have anything like a wristwatch or even something as simple as a notebook.  The moon is always with you.

A lunar month starts with the first sliver of light from a new moon and with practice you'd get to know how much time had passed from each additional sliver on the crescent moon.  A full moon would mean it is mid-month.  As the moon waned, you could count the days until the moon disappeared and you advanced to the next month.  Using a lunar calendar, if you know the month, all you need to do is look into the sky to know the date.

The ancient Babylonians were the first society to take long-term measurements of the moon.  They calculated the moon takes 29.53 days to do a complete cycle.  This means in a fully lunar-based calendar, a month always either 29 or 30 days.

This is exactly what the Babylonians did.  They created a 12-month lunar calendar with months of 29-30 days each and a year beginning with the first crescent moon of spring.  The months were given these names:

Lunar Month

Nisānu
Āru
Simanu
Dumuzu
Abu
Ulūlu
Tišritum
Samnu
Kislimu
Ṭebētum
Šabaṭu
Adār
 Addaru Arku

Western Month
March/Apr
April/May
May/June
June/July
July/Aug
Aug/Sept
Sept/Oct
Oct/Nov
Nov/Dec
Dec/Jan
Jan/Feb

Feb/March

Babylon Diety

Bel
Ea
Sīn
Tammuz
-
Ishtar
Shamash
Marduk
Nergal
Papsukkal
Adad
Erra
Assur

Hebrew Months
Nisan
Iyar
Sivan
Tammuz
Ab
Elul
Tishrei
Cheshvan
Kislev
Tebeth
Shebat
Adar

Adar I

Days in Month

30
29
30
29
30
29
30
29 or 30
30 or 29
29
30
29
     

354

Just because a lunar calendar is simple doesn't mean it doesn't have issues.  You might have already realized the biggest.  A lunar calendar totals 354 days in a 12 month year but a solar year is 365.25 days.  The Babylons fixed this by adding a 30 day month every third year after the month of Adār.  They also used the months of Samnu and Kislimu to keep the calendar in line.  The complete calendar was a 19-year cycle that did a good job of lining up to the moon but needed constant tinkering by scholars to keep the seasons in check.

One other thing you should note in the chart above is the similarity between the names of the Hebrew months and the Babylonian ones.  We aren't exactly sure when Judah started using Babylonian calendar but we know when it was definitely being used.

Babylon conquered most of today's Iraq in the late 7th BC century then conquered Judah in the early 6th century BC.   A series of Jewish rebellions led to an event the the Bible calls the Babylonian Captivity.

Situation in the Near East before Cyrus' invasion of Babylon and the Levant

Most scholars believe it was during this time that the Old Testament of the Bible was written down and codified.  The Jews remained in captivity until 538 BC when Cyrus of Persia defeated the Babylonians.

This was very fortunate for the Jewish people as Cyrus needed allies to keep th
e peace in the lands he had taken from the Babylonians.  Cyrus sent the Jewish nobles/priests back to Judah to rule in his stead.  These Jews returned with not only his declaration they should rule but also a new Holy book whose holy days used the Babylonian calendar.  This formed the basis for the calendar the Jewish people use to this day.

What Calendar did the early Christians use?

Christianity came into being during the time of Rome and as a result, the Christian Church has always used a Roman calendar.  During the Roman Republic era, they based their calendar on the Greeks/Babylonians but decided against fixing their calendar to the moon cycle.  Instead, they added days so their twelve-month calendar looked like this:

Martius	31
Aprilis	29
Maius	31
Iunius	29
Quintilis	31
Sextilis	29
September	29
October	31
November	29
December	29
Ianuarius	29
Februarius	28
	355
Mercedonius*

Note that the total number of days equals 355 which is why the month of Mercdonius (of 23 days) was occasionally added after Februarius to get things back in order.  Unfortunately, then just as now, politics intervened and the Pontifex Maximus would add a month to keep their friends in power longer or withhold a month so people they did not like would leave office quicker.

Julius Caesar

The calendar was another sign of the rot eating away at the core of the Roman Republic.  The republic had worked well for most of Rome's existence but the government was not well equipped to be able to deal the new realities.  In time, a series of military leaders rose claiming they could fix many of Rome's problems but they would need power over the Senate.

When Julius Caesar became dictator of Rome he worked to fulfill this promise.  He met with the best scientists of the day, and they decided the new calendar would be a mix of Egyptian and Greek methodology while still using the old Roman names.  Caesar's main goal was to make a calendar that would be aligned to the sun so it didn't need any human intervention.  The final result was put into practice in the year 46 BC.

46 BC is also known as the 'long year'.  Politics had so badly skewed the Roman calendar that Martius (March) was no longer in its traditional position of having the first new moon of the springtime.  To get it back in line, Caesar ordered a series of extra months which made the year of 46 BC a total of 445 days long.  One of Caesar's other reforms made Ianuarius the first month of the year.  The resultant calendar that began to be used in 45 BC should look much more familiar:

Ianuarius	31
Februarius*	28
Martius	31
Aprilis	30
Maius	31
Iunius	30
Julius	31
Sextilis	31
September	30
October	31
November	30
December	31
	365

A leap day was to be added automatically every fourth Februaius to make a Julian year 365.25 days long.  You should note the month of Quintilius was changed to Julius to honor the dictator that created this new calendar.  When Caesar's nephew Augustus took over after Julius he did the same and changed the name of Sextilis to honor himself.

It's good to be the king.  Mostly.  The downside is sometimes people want to stab you.  Julius knows.

How did the Christian Church come up with their calculation for Easter?

At its beginning, the early Christian Church didn't have a list of proscribed holy-days.  That's because the new religion was a movement of ideas from its believers instead of something where rules were dictated down.  Many early Christians celebrated Christ's resurrection on the same day the Jews celebrated Passover, the 14th day in the Jewish month of Nisan (March/April).  Others felt the festival of his resurrection should be on a Sunday in remembrance of the day of his resurrection.

Council of Nicea

By the year 325 AD, the religion had grown dramatically and differences among believers had caused enough infighting to the point of actual violence.  Emperor Constantine called a meeting of the Council of Nicea where priests from across the Roman Empire met and codified rules to end these disputes.

One of the decisions made at this meeting was the date of Easter.  Many Christians were celebrating on the day of Passover but other Christian scholars felt the Jewish calendar was out of alignment as Easter was then occurring before the first day of spring.  These Christians felt their scholars should determine the date of Passover using a Roman calendar and not leave it to the Jews to determine the date of their holiday.   It was also determined that Easter should be celebrated on a Sunday.

It was at this meeting the Christians decided that Easter would be celebrated on first Sunday after the first full moon after the vernal equinox (aka spring).

In conclusion

Hopefully, that answers any and all the questions about the date of Easter.  I know I've learned a lot writing this and could have written more as I simplified this for the sake of readability (I know...)  Before I close this posting, I do have one more thing to discuss since I learned it during my investigation of this subject.  It's a ...


BONUS SECTION!!!  I know I've confused you enough but I couldn't help it...


Why are there seven days in a week?  How did the days of the week get their names?

This also goes back to the Babylonians.  Their celestial observations noted that there were seven objects in the sky that moved faster than others.  Note - Neptune and Uranus can't be seen without a telescope nor can any smaller object that orbits our Sun.

The Babylonians ranked these seven heavenly 'gods' in importance from fastest to slowest:

Sun
Moon
Mars
Mercury
Jupiter
Venus
Saturn

Perhaps you've noticed something familiar?

Every seventh day of a month was set aside with certain gods getting their own holy-day.  This day was also known as an evil day since many activities weren't considered able to be performed lest you anger the gods.

The Babylonians reserved the 7th, the 14th, the 28th of each month was reserved for the worship specific gods.  The 19th of each month was also considered a holy-day as it was a 'week of weeks', 7 x 7 or 49 days since the start of a previous crescent moon.  They also held a holy-day called the Sabuttu (or day of mid-rest) on the 15th of each month when the moon was full.  Some think this holy-day inspired the Jewish word Shabbat or what in English is known as the Sabbath.

The Romans originally starting with an 8-day-week but they switched once the began interacting with the Eastern Mediterranean, most of whom (Greeks, Jews, Egyptians) had long used the Babylon concept of 7 day weeks.

The Romans even used the Babylon wording for their days of the week though they used the names from their gods instead of Babylonian ones.   When the Roman words were put into English they ever adapting Romans used Germanic gods instead of their own for the names for the days of the week - Tyr is the German god equated with Mars.  Wodin is Mercury.  Thor is Jupiter.  Frigga is Venus.

That is how English speakers derived our days of the week - Sunday, Moonday, Tyr's Day, Wodin's Day, Thor's Day, Frigga's Day, Saturnday.

Pretty cool huh?  Aren't you glad you read to the end?

Hello? HELLLLLOOOO?

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