Document Calc Gregorian in NEWS; fix manual a bit.

doc/misc/ChangeLog

+2012-11-22  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* calc.texi: Fix TeX issues with capitals followed by ".", "?", "!".
+	(Date Forms): Correct off-by-one error in explanation of
+	Julian day numbers.  Give Gregorian equivalent of its origin.
+
 2012-11-22  Jay Belanger  <jay.p.belanger@gmail.com>
 
 	* doc/misc/calc.texi (Date Forms): Mention the customizable

etc/ChangeLog

+2012-11-22  Paul Eggert  <eggert@cs.ucla.edu>
+
+	* NEWS: Document Calc changes for Gregorian calendar.
+
 2012-10-26  Nicolas Goaziou  <n.goaziou@gmail.com>
 
 	* refcards/orgcard.tex: Fix keybindings about

etc/NEWS

@@ -29,6 +29,20 @@ so we will look at it and add it to the manual.
 
 * Changes in Specialized Modes and Packages in Emacs 24.4
 
+** Calc
+
+*** Calc by default now uses the Gregorian calendar for all dates, and
+uses January 1, 1 AD as its day number 1.  Previously Calc used the
+Julian calendar for dates before September 14, 1752, and it used
+December 31, 1 BC as its day number 1; the new scheme is more
+consistent with Calendar's calendrical system and day numbering.
+
+*** The new variable `calc-gregorian-switch' lets you configure the
+date when Calc switches from the Julian to the Gregorian calendar.
+Nil, the default value, means to always use the Gregorian calendar.
+The value (YEAR MONTH DAY) means to start using the Gregorian calendar
+on the given date.
+
 +++
 ** New function `ses-rename-cell' to give SES cells arbitrary names.