Subject: Re: Non-Gregorian calendar programs?

From: [email-masked] (Mark James)
Date: Mon, 18 Oct 93 17:14:08 GMT

In article <[email-masked]> 
[email-masked] writes:
> A colleague in medieval history asked me if there were any PC-based 
> programs which allowed sky displays for dates based on pre-Gregorian 
> calendars, particularly  those in use in Europe from c. 1300-1600 A.D. 
> I wonder if anyone knows of any such programs - or at least a program 
> to convert easily between calendars (this is apparently non-trivial 
> since the conversion to Gregorian took pace over several decades and
> occured at various times in  different countries).

Not only that, but different countries started the year on different
dates (Christmas, January 1, March 1, Easter, etc.), and changed their 
minds frequently on this subject.  This is a topic that comes up
frequently in the genealogy newsgroup soc.roots; a guy named Tom Lincoln
has written a date-conversion program that is pretty thorough, as long
as you know what country or tiny kingdom you're dealing with.

If you're interested, contact Tom at <[email-masked]>.

-- 
Mark James  <[email-masked]>    *** Opinions, errors etc are mine. ***
Dialogic Corporation, 300 Littleton Road    | "Grown-ups are just obsolete
Parsippany NJ 07054, U.S.A.                 |  children, and the hell with
+1 201 334 1268 ext 438  Fax +1 201 334 1257|  them."  -- Dr. Seuss

---

From: [email-masked] (Julie Porter)
Date: Mon, 18 Oct 1993 19:19:45 GMT

In article <[email-masked]>, [email-masked] (Dave
Tholen) wrote:
> 
> Robert Mutel writes:
> 
> > A colleague in medieval history asked me if there were any PC-based programs
> > which allowed sky displays for dates based on pre-Gregorian calendars,
> > particularly  those in use in Europe from c. 1300-1600 A.D. I wonder if
> > anyone knows of any such programs - or at least a program to convert
> > easily between calendars (this is apparently non-trivial since the
> > conversion to Gregorian took pace over several decades and  occured at
> > various times in  different countries).
> 
> All of the calendar date to Julian Date conversion programs that I've ever
> seen force the switchover from the Julian calendar to the Gregorian calendar
> on 1582 October 4-15, but that's only when the Roman Catholic countries
> adopted the Gregorian calendar.  The conversion took more than several
> decades; Turkey didn't adopt it until 1927!
> 
> That's why when I set out to write my own calendar conversion routine, I
> added a flag that lets the user decide whether the date is in the Julian
> or Gregorian calendar system.  As far as I know, the Julian calendar was
> the one in use in Europe from 1300 to 1582, so this routine might be
> adequate for your purposes.  Of course, it isn't hard to convert.  The
> only differences between the two calendars are the leap days in the years
> evenly divisible by 100 (no leap day) and 400 (leap day).  This part is
> trivial.  Knowing when each country switched calendars isn't something I've
> ever seen built into software, though the Explanatory Supplement (old
> edition) has a printed listing that seems fairly complete.

Location is all important in calendar conversions. For England and the
American colonies. I have a very reliable date of the 3rd of September
1752. when 11 days were lost. Some other important points to remember in
calender correction that the day of the week does not change. also there
was no year zero in either bc or ad. Other points of confusion in the
Julian Calendar; the year begins on March 21. There is also no Feb 29 in
the Julian Calendar leapday was Feb 24 which was 48 hours long. This day
was known as the sextile, which is why some people refer to leap years as
bi-sextile. in that they have two days that are the sextile.
This information comes from _Geared to the Stars_ by Henery C. King, which
I have here in front of me.

In England prior to the coach travel of the 18th century. local time
prevailed. crossing the border into Scotland could even give you a diffrent
year. My impresion from studing complex clockwork is that for the most part
the day of week holds true. I imagin that there was enough communication
>from iterneate preist/travelers to see that Sunday was held pretty
consistantly. from village to village. The sky of course would be final
arbitrator as to the season. Those who needed a realy accurate date, ie a
monk or scholar, would use a three cycle system. This consisted of the 28
year solar cycle. The Epact, which appears to be different than the
astoronomical epact known as the _Golden Number based on luner phase at the
first of the year (which is different in the two calendars). The third
cycle is said to have derived from Rome. It is a 15 year cycle known as the
_Indiction_. IMO Astrology would only be used by those of rank, ie The King
and nobles. It agian in my own opionin would have had to much mythos
attached to it for the common man to feel comfortable using it as a
calendar for anything other than a birth, or death.

-jP