agenda: Fix org-duration-to-minutes error (take 2)

* lisp/org.el (org-stamp-time-of-day-regexp): Limit match group 2 to
first time.
* lisp/org-agenda.el (org-agenda-format-item): Compute duration before
formatting time with `org-get-time-of-day'.

lisp/org-agenda.el

@@ -6656,10 +6656,6 @@ Any match of REMOVE-RE will be removed from TXT."
 			   (= (match-beginning 0) 0)
 			 t))
 	      (setq txt (replace-match "" nil nil txt))))
-	  ;; Normalize the time(s) to 24 hour
-	  (when s1 (setq s1 (org-get-time-of-day s1 'string t)))
-	  (when s2 (setq s2 (org-get-time-of-day s2 'string t)))
-
 	  ;; Try to set s2 if s1 and
 	  ;; `org-agenda-default-appointment-duration' are set
 	  (when (and s1 (not s2) org-agenda-default-appointment-duration)
@@ -6668,12 +6664,13 @@ Any match of REMOVE-RE will be removed from TXT."
 		   (+ (org-duration-to-minutes s1 t)
 		      org-agenda-default-appointment-duration)
 		   nil t)))
-
 	  ;; Compute the duration
 	  (when s2
 	    (setq duration (- (org-duration-to-minutes s2)
-			      (org-duration-to-minutes s1)))))
-
+			      (org-duration-to-minutes s1))))
+          ;; Normalize the time(s) to 24 hour
+	  (when s1 (setq s1 (org-get-time-of-day s1 'string t)))
+	  (when s2 (setq s2 (org-get-time-of-day s2 'string t))))
 	(when (string-match org-tag-group-re txt)
 	  ;; Tags are in the string
 	  (if (or (eq org-agenda-remove-tags t)

lisp/org.el

@@ -4106,7 +4106,7 @@ groups carry important information:
 (defconst org-stamp-time-of-day-regexp
   (concat
    "<\\([0-9]\\{4\\}-[0-9]\\{2\\}-[0-9]\\{2\\} +\\sw+ +\\)"
-   "\\([012][0-9]:[0-5][0-9]\\(-\\([012][0-9]:[0-5][0-9]\\)\\)?[^\n\r>]*?\\)>"
+   "\\([012][0-9]:[0-5][0-9]\\)\\(-\\([012][0-9]:[0-5][0-9]\\)\\)?[^\n\r>]*?>"
    "\\(--?"
    "<\\1\\([012][0-9]:[0-5][0-9]\\)>\\)?")
   "Regular expression to match a timestamp time or time range.