'cal 9 1752' and emacs calendar disagree

'cal 9 1752' and emacs calendar disagree

[Leon]

Hi there,

For some historical reasons¹, September 1752 is a special month that
has no 3 - 13 dates. As you can see, 'cal 9 1752' will gives

   September 1752   
Su Mo Tu We Th Fr Sa
       1  2 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30


While emacs calendar gives:

   September 1752    
Su Mo Tu We Th Fr Sa 
                1  2 
 3  4  5  6  7  8  9 
10 11 12 13 14 15 16 
17 18 19 20 21 22 23 
24 25 26 27 28 29 30

Is this a bug?

Footnotes: 
¹  http://www.farid-hajji.net/fun/cj-cal91752.html
-- 
Leon

Re: 'cal 9 1752' and emacs calendar disagree

[Ed Reingold]

No, it is not a bug.  The odd Sept 1752 was only that way in England and her 
colonies--not in general.  It is the Unix cal program that is in error.  The 
Emacs calendar shows the Gregorian calendar, period.  But it allows one to get 
dates on many other calendars as well, such as the Julian.  What cal gives is 
the first part of the month on Julian calendar and the latter part on the 
Gregorian--that is nonsense.

The date the switch was made is geographically dependent and stretched over a 
period of hundreds of years.


> 
> Hi there,
> 
> For some historical reasons¹, September 1752 is a special month that
> has no 3 - 13 dates. As you can see, 'cal 9 1752' will gives
> 
>    September 1752   
> Su Mo Tu We Th Fr Sa
>        1  2 14 15 16
> 17 18 19 20 21 22 23
> 24 25 26 27 28 29 30
> 
> 
> While emacs calendar gives:
> 
>    September 1752    
> Su Mo Tu We Th Fr Sa 
>                 1  2 
>  3  4  5  6  7  8  9 
> 10 11 12 13 14 15 16 
> 17 18 19 20 21 22 23 
> 24 25 26 27 28 29 30
> 
> Is this a bug?
> 
> Footnotes: 
> ¹  http://www.farid-hajji.net/fun/cj-cal91752.html
> -- 
> Leon
> 
> 
> 
> _______________________________________________
> Emacs-devel mailing list
> Emacs-devel@gnu.org
> http://lists.gnu.org/mailman/listinfo/emacs-devel

Re: 'cal 9 1752' and emacs calendar disagree

[Kim F. Storm]

Ed Reingold <reingold@emr.cs.iit.edu> writes:

> No, it is not a bug.  The odd Sept 1752 was only that way in England and her 
> colonies--not in general.  It is the Unix cal program that is in error.  The 
> Emacs calendar shows the Gregorian calendar, period.  But it allows one to get 
> dates on many other calendars as well, such as the Julian.  What cal gives is 
> the first part of the month on Julian calendar and the latter part on the 
> Gregorian--that is nonsense.
>
> The date the switch was made is geographically dependent and stretched over a 
> period of hundreds of years.

For minute details, see http://www.tondering.dk/claus/cal/calendar28.txt

-- 
Kim F. Storm <storm@cua.dk> http://www.cua.dk

Re: 'cal 9 1752' and emacs calendar disagree

[Richard Stallman]

      What cal gives is 
    the first part of the month on Julian calendar and the latter part on the 
    Gregorian--that is nonsense.

It is not be quite nonsense, if it reflects the actual calendar used
in England and its colonies at the time.  However, England and its
colonies were not the whole world, so it doesn't make sense for a
calendar program to display in a way that is right for them and wrong
for everywhere else.  (I would guess this was originally done because
Unix was written in the US, which was formerly part of England's
colonies.)

It would be nice if Emacs could display pure Julian calendar for all
dates, as an option.

And we could then imagine, as further options, to display the calendar
as it was used in England, or some other place, including whatever
transition period there was in that place.

Re: 'cal 9 1752' and emacs calendar disagree

[Nic James Ferrier]

Leon <sdl.web@gmail.com> writes:

> Hi there,
>
> For some historical reasons¹, September 1752 is a special month that
> has no 3 - 13 dates. As you can see, 'cal 9 1752' will gives
>
>    September 1752   
> Su Mo Tu We Th Fr Sa
>        1  2 14 15 16
> 17 18 19 20 21 22 23
> 24 25 26 27 28 29 30
>
>
> While emacs calendar gives:
>
>    September 1752    
> Su Mo Tu We Th Fr Sa 
>                 1  2 
>  3  4  5  6  7  8  9 
> 10 11 12 13 14 15 16 
> 17 18 19 20 21 22 23 
> 24 25 26 27 28 29 30
>
> Is this a bug?

No. Unix cal is badly broken in respect of understood calendrical
systems.

Ordinary calendars are consistent within a calendrical system. So if
we accept and use the Gregorian Calendar we count backwards with it as
well as counting forwards.

It does not matter that in a particular locale the Gregorian system
was started on a particular date. Only that a particular locale uses 
the Gregorian system.

Unix cal is only right if you happen to be English or you are American
and accept England's conversion to the Gregorian calendar as the date
when the colonies were converted as well.

But if you are Russian or French or Mexican there is absolutely no
reason to think of cal's 9 1752 behaviour as being in any way
sensible.


-- 
Nic Ferrier
http://www.tapsellferrier.co.uk   for all your tapsell ferrier needs

Re: 'cal 9 1752' and emacs calendar disagree

[Andreas Schwab]

Leon <sdl.web@gmail.com> writes:

> For some historical reasons¹, September 1752 is a special month that
> has no 3 - 13 dates.

Depends on where you live.  The georgian calendar was first adopted in
1582, but it took until 1923 that all European countries switched to it.

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
PGP key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: 'cal 9 1752' and emacs calendar disagree

[Leon]

Thank you all for explaining this.

-- 
Leon

Re: 'cal 9 1752' and emacs calendar disagree

[Nic James Ferrier]

Leon <sdl.web@gmail.com> writes:

> Thank you all for explaining this.

/8->

It's like being corrected by 20 or so History of Calender Systems
Professors. Kind of dusty but polite.


-- 
Nic Ferrier
http://www.tapsellferrier.co.uk   for all your tapsell ferrier needs