Calc now uses the Gregorian calendar for all dates,

and uses January 1, 1 AD as its day number 1.
* doc/misc/calc.texi (Date Forms): Document this.

* lisp/calc/calc-forms.el (math-julian-date-beginning)
(math-julian-date-beginning-int): Implement this.

2 files changed, 11 insertions, 6 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index f9e9217fe10..4c3f4e51ffb 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,8 @@
+2012-11-17  Paul Eggert  <eggert@cs.ucla.edu>
+
+        * calc/calc-forms.el (math-julian-date-beginning)
+        (math-julian-date-beginning-int): Implement [new date numbering].
+
 2012-11-17  Juanma Barranquero  <lekktu@gmail.com>
 
         * descr-text.el (quail-find-key):
diff --git a/lisp/calc/calc-forms.el b/lisp/calc/calc-forms.el
index c1f6d03db80..d1df20c697c 100644
--- a/lisp/calc/calc-forms.el
+++ b/lisp/calc/calc-forms.el
@@ -656,13 +656,13 @@ in the Gregorian calendar."
                (setcdr math-fd-dt nil))
           fmt))))
 
-(defconst math-julian-date-beginning '(float 17214235 -1)
-  "The beginning of the Julian calendar,
-as measured in the number of days before January 1 of the year 1AD.")
+(defconst math-julian-date-beginning '(float 17214225 -1)
+  "The beginning of the Julian date calendar,
+as measured in the number of days before December 31, 1 BC (Gregorian).")
 
-(defconst math-julian-date-beginning-int 1721424
-  "The beginning of the Julian calendar,
-as measured in the integer number of days before January 1 of the year 1AD.")
+(defconst math-julian-date-beginning-int 1721423
+  "The beginning of the Julian date calendar,
+as measured in the integer number of days before December 31, 1 BC (Gregorian).")
 
 (defun math-format-date-part (x)
   (cond ((stringp x)