Re: The Emacs Calculator and calendar

[Paul Eggert <eggert@cs.ucla.edu>]

On 10/09/2012 08:47 AM, Richard Stallman wrote:

> a crucial question for this purpose: defining a "Hungarian" calendar
> domain that might be useful for people today who are thinking about
> dates in the Hungarian past.

Good point.  So, as I understand it, the case you're worried
about is a source where the author's practice is something
like the following:

   This book uses the Gregorian calendar for dates from 14
   September 1752 onwards, and the Julian calendar starting
   on January 1 for dates before that.  The calendar is not
   otherwise indicated.

No doubt some books exist like that, but in my experience
the following sorts of rules are more typical:

  "For the purposes of this book, all dates are given using
   the modern Gregorian calendar unless specifically
   followed by the O.S. designation."
     -- David Marley, Wars of the Americas, ABC-CLIO (2008),
	page xiii.

  "I distinguish old style (o.s.) from "new style" (n.s.)
   dates in chapter 1, but in later chapters the reader
   should understand that all dates are modern or new style,
   unless otherwise indicated."
     -- Allan Everett Marble, Surgeons, Smallpox, and the Poor
	(McGill-Queens, 1997), p. 11

  "In this book Continental dates in the period 1582-1752
   can generally be assumed to be given according to the
   Gregorian system, and British (and American) dates of the
   period according to the Julian system, but with the year
   in all cases deemed to begin on 1 January, not 25 March.
   However, when dates are taken from a great variety of
   sources, as they are in a book like this, it is not
   always possible to be sure which system has been used"

   -- Ian Chilvers, The Oxford Dictionary of Art (OUP, 2004), p. vii.

That is, when there is possible confusion about the calendar,
there is a book-specific set of rules that typically cannot
easily be reduced to the Unix cal rule, or to a rule that
is more-easily programmable than what Emacs calendar already
does.