--- calendar.el	2013-02-06 10:28:54.679401343 -0800
+++ calendar.el.new	2013-02-06 10:28:25.738455568 -0800
@@ -1417,6 +1417,7 @@
 
 (defun calendar-ensure-newline ()
   "Move to the next line, adding a newline if necessary."
+  (delete-trailing-whitespace  (line-beginning-position) (line-end-position) )
   (or (zerop (forward-line 1))
       (insert "\n")))
 
@@ -1499,7 +1500,8 @@
                 (/= day last))
        (calendar-ensure-newline)
        (setq day (1+ day))              ; first day of next week
-       (calendar-insert-at-column indent calendar-intermonth-text trunc)))))
+       (calendar-insert-at-column indent calendar-intermonth-text trunc)))
+   (delete-trailing-whitespace  (line-beginning-position) (line-end-position))))
 
 (defun calendar-redraw ()
   "Redraw the calendar display, if `calendar-buffer' is live."