On 2009 May 1, at 11:41 , Palmen, KEV (Karl) wrote:
Irv wrote: On the contrary, I have shown that March 21st was the correct date, assuming it was reckoned at Alexandria with the calendar day starting at sunset, as was the practice at the time, see <http://www.sym454.org/mar21/>. Also, the ecclesiastical equinox refers to the first day that is in the spring season, which was without doubt March 21st in 325 AD in Alexandria.
If this were so for the Julian Calendar, it would have been March 22 for the Proleptic Gregorian calendar. Four 400-year cycles later in 1925 the equinox was March 21st 03:12 according to http://stellafane.org/misc/equinox.html . ,so giving a date of March 21st (12th hour) in Alexandria. So a drift of over half a day would be necessary to make it 22nd March in the proleptic Gregorian 1600 years earlier (I’ve chosen a multiple of 400 years to eliminate calendar jitter). This is sufficient argument to show that the date was wrong. Also I recall another E-mail that said that the date was got from Ptolemy who reckoned that the tropical year was 1/300 day short of 365 ¼ days.
Irv replies: I've never heard of there ever having been any intention of making the equinox land on March 21st in 325 AD on the proleptic Gregorian calendar. This seems implausible to me.
Notwithstanding Karl's argument, the actual northward equinox reckoned for the meridian of Alexandria was just before noon on March 21st on the proleptic Gregorian calendar, so no problem there.
Julian March 21st would have started at the sunset about 6+1/4 hours later, making Julian March 21st the ecclesiastical first day of spring.
-- Irv Bromberg, Toronto, Canada
