Gregorian vs. Julian Millennium - off topic

tuisto at tuisto at
Fri Jan 4 03:35:11 PST 1980

At 01:28 PM 1/4/00 -0500, Bob Mauritsen wrote:

>Consider also that when the Gregorian calendar was instituted,

>there was a huge adjustment made in the date. So, if you are

>counting the absolute number of days that have transpired, then

>Jan 1, 2001, is not the actual start of a millennium, either. :)

Actually, the adjustment of "skipping" 10 days in 1582 (or more for
countries that adopted the Gregorian calendar later) corrected the date so
that Jan 1, 2001 *does* mark the actual passage of 1000 solar years since
AD 1/1/1. Without the Gregorian reforms of the adjustment of the date and
the correction of omitting leapdays in 3 out of 4 years ending in 00, the
absolute number of days in 1000 solar years would still end on the date we
call December 31, 2000, but it would be called December 18 in the Julian
calender, making December 19, 2000 the start of the new millennium in the
Julian calendar (if I counted correctly). The Julian calendar has "lost" 3
more days since 1582 by having leapdays in 1700, 1800, and 1900, making it
13 days "behind" the Gregorian calendar, which does not have leap days in
those years.

The "skipping" of 10 days in 1582 served to put the spring equinox (a
defined point in the solar year) back on March 21 where the Council of
Nicaea had determined it should be in 325. A caveat to the statement above
that 1/1/2001 occurs 1000 solar years after 1/1/1 is that for this to be
true dates in the Julian calendar prior to 325 should also be corrected so
that spring equinox falls on March 21. I am uncertain how chronologists
handle this correction, since the uncorrected Julian calendar has been in
use since 45 BC.
At that time Sosigenes set up the calendar so that Spring equinox would
fall on March 25 (and winter solstice on December 25), although his
calculation of when the equinox occurred was apparently off by a day. Do
historians adjust dates in this period by three days when they adjust the
designation of the year (the notion of dating from the year of the birth of
Jesus didn't originate until 532 and took a few hundred years to catch on)
or do they correct only the year and use the "uncorrected" month and day?
To be safe start celebrating on December 28 and keep it up into January 2001.

Paul Talbert
Hillman City, Seattle

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