[soc.religion.christian] Calendars

hwt@bnr-fos.uucp (Henry Troup) (09/07/89)

In article <Sep.4.05.56.30.1989.25690@athos.rutgers.edu> kolassa@ysidro.uchicago.edu (Kolassa) writes:
>
>I think the above is correct; however, the number of days by which the
>Julian and Gregorian calendars disagree should be increasing.  Does anyone
>know why the Jan 6 date is fixed, or know that my explanation is 
>wrong?
>
>John Kolassa
On average, the two calendars slip one day further out every 72 years.
However, as the difference occur on the calculation of leap years at
the last year of the century, the slip occured all at once once in 1900,
and the next slip is 2100 AD.  (2000 AD is a leap year by both systems,
I think).

firth@sei.cmu.edu (09/11/89)

The difference between the Julian and Gregorian calendars is that
the former prescibes that every fourth year be a leap year, while
the latter requires a century year (xx00) to be a leap year only
every fourth century.

Accordingly, 1900 was a leap year in the Julian calendar but not
in the Gregorian, and so the two calendars diverged by a further
day and are now 13 days apart.  Since 2000 is divisible by 400,
both calendars consider it to be a leap year, so the next one-day
change will be in 2100, unless by then we have yet again revised
the calendar.

Clearly, the average rate of divergence is 3 days in 400 years,
or about 1 day every 133 years.

The length of the mean solar year is approx 365.2422 days, so the
Julian calendar (365.25) falls behind the sun by 0.78 days per
century, and the Gregorian (365.2425) falls behind by 0.03 days
per century.  That is why 10 days [*] were dropped when the
changeover occurred: the accumulated drift of about 1400 years
had to be corrected.

[*] if you changed in +XV, that is.  When Britain changed the
    difference was 11 days; Russia in 1923 had to drop 13.

rock@sun.com (Bill Petro) (09/11/89)

!hwt@bnr-fos.uucp (Henry Troup) writes:


>In article <Sep.4.05.56.30.1989.25690@athos.rutgers.edu> kolassa@ysidro.uchicago.edu (Kolassa) writes:
>>
>>I think the above is correct; however, the number of days by which the
>>Julian and Gregorian calendars disagree should be increasing.  Does anyone
>>know why the Jan 6 date is fixed, or know that my explanation is 
>>wrong?
>>
>>John Kolassa
>On average, the two calendars slip one day further out every 72 years.
>However, as the difference occur on the calculation of leap years at
>the last year of the century, the slip occured all at once once in 1900,
>and the next slip is 2100 AD.  (2000 AD is a leap year by both systems,
>I think).

"Everyone knows" Jesus must have been born on December 25, A.D. 1, but
it is not quite that simple, and certainly this date is wrong.  Herod
the Great (who killed all the babies in Bethlehem younger than 2 years
of age) died in the spring of 4 B.C., and the king was very much alive
during the visit of the Wise Men (Magi) in the Christmas story.
Therefore Jesus would have been born before this time, anywhere from
7-4 B.C. (Before Christ, or before himself).

Why then is our calender about 5 years off?  It was a sixth-century
Roman monk-mathematician-astronomer named Dionysis Exeguus (Dionysis
the Little) who unknowingly committed what has become history's
greatest numerical error in terms of cumulative effect.  In reforming
the calender to pivot around the birth of Christ, he dated the Nativity
in the year 753 from the founding of Rome (753 a.u.c.), when in fact
Herod died only 749 years after Rome's founding.  The result of
Dionysis' chronology, which remains current, was to give the correct
traditional date for the founding of Rome, but one that is at least 4
to 7 years off for the birth of Christ.

     Bill Petro  {decwrl,hplabs,ucbvax}!sun!Eng!rock
"UNIX for the sake of the kingdom of heaven"  Matthew 19:12

crowe@sci.ccny.cuny.edu (Daniel Crowe) (09/13/89)

In article <Sep.11.01.47.37.1989.4389@athos.rutgers.edu> rock@sun.com (Bill Petro) writes:
>Herod the Great (who killed all the babies in Bethlehem younger than 2
>years of age)

Actually, Herod ordered the death of all males least than one year old if
you use today's exclusive reckoning (i.e., a person is age zero at birth).
People used inclusive reckoning (i.e., a person was age one at birth) at
the time of Jesus' birth.

-- 
Daniel (God is my judge) | "Everyone should be quick to listen, slow to
physics graduate student |  speak and slow to become angry, for man's
City College of New York |  anger does not bring about the righteous
crowe@sci.ccny.cuny.edu  |  life that God desires." (James 1:19-20,NIV)

jackg@tekirl.labs.tek.com (Jack Gjovaag) (09/15/89)

In article <Sep.13.03.23.10.1989.11300@athos.rutgers.edu> crowe@sci.ccny.cuny.edu (Daniel Crowe) writes:
>
>In article <Sep.11.01.47.37.1989.4389@athos.rutgers.edu> rock@sun.com (Bill Petro) writes:
>>Herod the Great (who killed all the babies in Bethlehem younger than 2
>>years of age)
>
>Actually, Herod ordered the death of all males least than one year old if
>you use today's exclusive reckoning 

I am curious about what non-biblical records for this event
exist.  I would like to know more about Herod's reason for
the order, when it occurred and how many infants might
have been involved.  Any sources??

  Jack Gjovaag
  Tek Labs

[A commentary I checked says that there is no source for this outside
Matthew.  The action is consistent with the character of Herod as
known from other historical sources.  --clh]