Why celebrate Easter at a different time than Roman Catholics?

[Fone_Bone_2001]

Fone Bone 2001.

The Eastern Church using the old calendar calculates Pascha according to the actual, astronomical full moon and the actual equinox as observed along the meridian of Jerusalem and also applies the formula so that Easter always falls after Passover. So essentially Orthodox Pascha will always occur on the first Sunday after the first full moon following the Vernal Equinox after Passover. Gauss’ formula for the Paschal Full Moon reduces to Julian 20 March + (((YR MOD 19)*19+16) MOD 30).

The Gregorian method does not use the actual astronomically correct date for the Vernal Equinox, but March 21, and Easter sometimes precedes Passover (even by weeks). Gregorian Easter can never occur before March 22 or later than April 25.

So Orthodox Julian Pascha can be up to 5 weeks later than the Gregorian Easter. All that has to happen is to have a mismatch of the equinox to push it a month later, and then an additional week can occur because of Passover.

peltiertech.com/WordPress/calculating-easter/

moonwise.co.uk/neweaster.php

Oh, I see.

Are you absolutely certain that the calculations for Julian Easter begin with the astronomical equinox? The formula you gave said “Julian March 20” is the starting point… but Julian March 20 is Gregorian April 2, which is always well after the real/astronomical vernal equinox.

This link shows a table that lists side-by-side Gregorian Easter, Julian Easter, and “astronomical Easter” (i.e. Easter if the real northern hemisphere’s astronomical equinox and the actual full moon over the meridian of Jerusalem were used instead of ecclesiastical tables), and Gregorian Easter and astronomical Easter almost always coincide (they do differ every once in awhile), whereas Julian Easter and astronomical Easter are pretty much only the same if Julian and Gregorian Easter coincide as well.

Why is that?

 

[Vico]

Oh, I see.

Are you absolutely certain that the calculations for Julian Easter begin with the astronomical equinox? The formula you gave said “Julian March 20” is the starting point… but Julian March 20 is Gregorian April 2, which is always well after the real/astronomical vernal equinox.

This link shows a table that lists side-by-side Gregorian Easter, Julian Easter, and “astronomical Easter” (i.e. Easter if the real northern hemisphere’s astronomical equinox and the actual full moon over the meridian of Jerusalem were used instead of ecclesiastical tables), and Gregorian Easter and astronomical Easter almost always coincide (they do differ every once in awhile), whereas Julian Easter and astronomical Easter are pretty much only the same if Julian and Gregorian Easter coincide as well.

Why is that?

Looks like I misunderstood. A second source stated that the Orthodox do an exact calculation, (but metonic will not align every year). The second source, at the Moonwise site the formula is for the Orthodox Paschal Full Moon and the comment with it is: “The Orthodox Churches also celebrate Easter (Pascha) on the Sunday after the Paschal Full Moon. … Julian 20 March is Gregorian 2 April until 2099”. Then he gives that formula. So it is later than the vernal equinox. There will be agreement about every three years because of the metonic cycle. The 19 year metonic cycle has an incalation month added every 3 years because each year is short by about 1/3 month. So the Orthodox calculation uses the metonic cycle.

That is a great table at the link you gave.

 

[mistergeorge]

the thing that is odd are the dreams

 

[Fone_Bone_2001]

Looks like I misunderstood. A second source stated that the Orthodox do an exact calculation, (but metonic will not align every year). The second source, at the Moonwise site the formula is for the Orthodox Paschal Full Moon and the comment with it is: “The Orthodox Churches also celebrate Easter (Pascha) on the Sunday after the Paschal Full Moon. … Julian 20 March is Gregorian 2 April until 2099”. Then he gives that formula. So it is later than the vernal equinox. There will be agreement about every three years because of the metonic cycle. The 19 year metonic cycle has an incalation month added every 3 years because each year is short by about 1/3 month. So the Orthodox calculation uses the metonic cycle.

That is a great table at the link you gave.

Ah, okay, that makes sense. Thanks, Vico!