Compute negative clock intervals correctly.

Patch by Chris Leyton.

lisp/ChangeLog

@@ -1,3 +1,8 @@
+2008-10-17  Carsten Dominik  <dominik@science.uva.nl>
+
+	* org.el (org-clock-update-time-maybe): Compute negative clock
+	intervals correctly.
+
 2008-10-15  James TD Smith  <ahktenzero@mohorovi.cc>
 
 	* org.el (org-add-log-setup): Only skip drawers if the are

lisp/org.el

@@ -2544,11 +2544,13 @@ Otherwise, return nil."
 		      (apply 'encode-time (org-parse-time-string te)))
 		     (time-to-seconds
 		      (apply 'encode-time (org-parse-time-string ts))))
+		sign (if (< s 0) "-" "")
+		s (abs s)
 		h (floor (/ s 3600))
 		s (- s (* 3600 h))
 		m (floor (/ s 60))
 		s (- s (* 60 s)))
-	  (insert " => " (format "%2d:%02d" h m))
+	  (insert " => " (format "%s%2d:%02d" sign h m))
 	  t))))))
 
 (defun org-check-running-clock ()