How Easter is Calculated


We are now going to see the difference in calculavstion between Easter and Pesach, and how different Easter is from the simple date that God chose for Pesach.

What determines the date of Easter?

Easter’s date calculaton starts theoretically with the spring equinox – the point in the year when the day and night are of equal length.
If the full moon after the equinox is on a Sunday, then Easter is on the following Sunday.
The formula was decided after much controversy among early Christians in 325 under Constantine.
The festival cannot fall earlier than 22 March or later than 25 April.

Easter is related to the pagan feast of the goddess known in Mesopotamia as Ishtar, the idols of which were known in the Bible as Ashtaroth, associated with Baal (the idols of which were called Baalim).

1 Samuel 7:4  Then the children of Israel did put away Baalim and Ashtaroth, and served the LORD only.
1 Samuel 12:10  And they cried unto the LORD, and said, We have sinned, because we have forsaken the LORD, and have served Baalim and Ashtaroth: but now deliver us out of the hand of our enemies, and we will serve thee.

The Spring Equinox does not determine the date:

Easter is not calculated according to the actual Spring Equinox. 
It’s based on the one defined by the Council of Nicea in 325AD which defined it to be March 21.
In those days the Julian Calendar was in use.
The Julian Calendar’s “March 21″ occurs many days after the Gregorian Calendar’s “March 21.” 
So the full moon doesn’t happen at the same time in relation to the defined date of Spring Equinox as it does on the Gregorian Calendar.

The full moon too does not determine the date.

Easter Sunday is the Sunday following the Paschal Full Moon date (PFM) for the year.  

(Paschal is pronounced “PAS-KUL”, not “pas-chal”).  

To shorten the explanation, we will use acronyms.

  • PFM = Paschal Full Moon
  • EFM = Ecclesiastical Full Moon
  • AFM = Astronomical Full Moon

In June 325 A.D. astronomers approximated the AFM dates for the Christian church, calling them Ecclesiastical Full Moon (EFM) dates.  
From 326 A.D. the PFM date has always been the EFM date after March 20 (which was the equinox date in 325 A.D.)
From 1583, each PFM date differs from an AFM date usually by no more than 1 date, and never by more than 3 dates.   (Each AFM is actually a two-date event due to world time zones.  But each PFM is a one-date event world-wide.)

Having got our terminology and acronyms clear, we can look at the Roman Catholic formula for calculating the Easter date.

First some explanatory notes:

‘ Given the Year as a four digit number in the range 1700 – 2299
‘ Calculate Day and Month of Easter Sunday

‘ Note 1: The algorithm has not been tested outside the range 1700 – 2099.
‘ Note 2: The \ operator in the following formula performs integer division without remainder.
‘ Note 3: The mod operator yields the remainder after divison.
‘ Note 4: The date returned by the formula is the Gregorian Calendar date (the one we use now), even for dates in the 18th Century.

The actual mathematical formula using the above notations expressed in steps for easy calculation:

a = Year mod 19;
b = Year \ 100;
c = Year mod 100;
d = b \ 4;
e = b mod 4;
f = c \ 4;
g = c mod 4;

h = (b + 8)\25;
i = (b – h + 1)\3;
j = (19*a + b – d – i + 15) mod 30;
k = (32 + 2*e + 2*f – j – g) mod 7;
m = (a + 11*j + 22*k) \ 451;
n = j + k – 7*m + 114;

Month = n\31;
Date = (n mod 31) + 1;

The last two lines return the month and date of Easter for the current year.

To follow the calculations on a spreadsheet, click here. I must confess that the spreadsheet as attached comes out as “read only” and the target year is the current year 2012. If you want to use it to find the date of Easter in any other year, you may have to “save as” as another spreadsheet and change the Year figure there, to get the Easter date for that year.

Contrast the simplicity of God’s Passover Calculation
against the complexity of the Catholic Easter Calculation.

God’s Passover Calculation

Nissan 1 is New Moon in Spring
Nissan 14 is Passover

What we are contrasting is God’s calendar vs Man’s

Nissan (Abib) is a month prescribed by God. Starts on the new moon in Spring. This is God’s calendar.
Passover falls every year on the 14th Nissan – the same date each year on the Jewish Calendar.
Easter is not calculated as the 14th Nissan.
Falls on a different date each year both in the Jewish and Gregorian calendar.

Ultimately, the issue is one of Obedience to God.

This is the Transitional Generation.
Today, every church is being invited by God to follow His calendar when it comes to worship.

Yeshua, our Messiah, Savior and Lord, said:

Mark 12:17  And Jesus answering said unto them, Render to Caesar the things that are Caesar’s, and to God the things that are God’s. And they marvelled at him.

Will we obey His instruction? or the instructions of the institutional churches (which most non-institutional churches also follow)?


Back to Passover





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