Newsgroups: bit.listserv.catholic
Date:         Fri, 22 Jan 1993 17:40:31 -0500
From:         Michael I Bushnell <mib@GNU.AI.MIT.EDU>
Subject: Easter Date... West Vs. East -- nothing to do with
              Julian/Gregorian!
              22 Jan 93 14:06:32 PST <9301222206.AA10281@enet-gw.pa.dec.com>

   Date: Fri, 22 Jan 93 14:06:32 PST
   From: John R. Covert  22-Jan-1993 1708 <covert@covert.enet.dec.com>
   Apparently-To: mib@gnu.ai.mit.edu

   >Do Eastern Rite Catholics use the Gregorian calendar (and its date of
   >Easter) or the Julian calendar?

   I'll leave the full answer to this to someone else; see the note for
   Maronite Catholics in the next paragraph.

   The discrepancy in the date of Easter between the Eastern and Western
   Church has nothing to do with the Gregorian vs. Julian calendar; it
   has to do with how the 14th day of the lunar month is calculated, with
   eastern tradition starting the day in the evening and western tradition
   starting the day at midnight.  Interestingly, although the Maronite day
   starts in the evening (keeping semitic tradition), Maronites use the
   Western calculation for the date of Easter.

That's not the only difference.  The two calendars also disagree about
when March 21st occurs, and about calendrical new moons (as
distinguished from astronomical new moons, which might be up to a day
off).

In the sentence, which is essentially the same as the Nicene decision:
"Easter Day is always the Sunday after the full moon that occurs on or
after the spring equinox on March 21" there are the following
ambiguities:

When does March 21st occur?  This varies, depending on whether one
observes the Gregorian leap year correction or not.  The Western
Church is Gregorian, the Eastern is Julian.

What are the boundaries of the day?  This varies, depending upon
one starts the day in the evening or at midnight.  Except for the
Maronites, this varies as you mention.

When do the full moons occur?  The Julian calendar (as used in the
Church) has calendrical New Moons, which follow a 19 year cycle.  This
cycle is not actually correct, and varies through the centuries.  The
Gregorian reform also modified the calendrical New Moons to conform
more closely to astronomical (real) new moons.  It is this "ancient
ecclesiastical computation" to which the BCP refers.  The Eastern
church retains the old 19-year cycle of the Julian calendar, the
Western observes the Gregorian reform.

As a simpler example than easter, the date of Christmas is December
25, everywhere, and the date of Epiphany is January 6, everywhere.
But the Eastern Orthodox celebrate Christmas on Gregorian January 5,
because that is Julian December 25, and they celebrate Epiphany on
Gregorian January 18, because that is Julian January 6.

My question then is, do the Eastern Rite Catholics use the Gregorian
Calendar or the Julian Calendar?  The parenthetical comment was meant
to ask, as well, what the Easter rules (full moon dating and
day-start-time) are.

In many polemics against the West by the East, the Gregorian reform
enters strongly into it, as one more papal abuse of the Council of
Nicaea.  As a result, I'm interested in whether Eastern Rite Catholics
keep the Eastern computations or not.

        -mib
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