Improve error reporting on bad time stamps during agenda construction

* lisp/org.el (org-time-string-to-time):
(org-time-string-to-absolute): Add optional arguments BUFFER and POS
for error reporting.
* lisp/org-agenda.el (org-get-all-dates):
(org-agenda-get-timestamps):
(org-agenda-get-deadlines):
(org-agenda-get-scheduled):
(org-agenda-get-blocks): Call time stamp parsing functions with
information on where the timestamp was taken from.

lisp/org-agenda.el

@@ -3431,22 +3431,26 @@ When EMPTY is non-nil, also include days without any entries."
   (let ((re (concat
 	     (if pre-re pre-re "")
 	     (if inactive org-ts-regexp-both org-ts-regexp)))
-	 dates dates1 date day day1 day2 ts1 ts2)
+	 dates dates1 date day day1 day2 ts1 ts2 pos)
     (if force-today
 	(setq dates (list (org-today))))
     (save-excursion
       (goto-char beg)
       (while (re-search-forward re end t)
 	(setq day (time-to-days (org-time-string-to-time
-				 (substring (match-string 1) 0 10))))
+				 (substring (match-string 1) 0 10)
+				 (current-buffer) (match-beginning 0))))
 	(or (memq day dates) (push day dates)))
       (unless no-ranges
 	(goto-char beg)
 	(while (re-search-forward org-tr-regexp end t)
+	  (setq pos (match-beginning 0))
 	  (setq ts1 (substring (match-string 1) 0 10)
 		ts2 (substring (match-string 2) 0 10)
-		day1 (time-to-days (org-time-string-to-time ts1))
-		day2 (time-to-days (org-time-string-to-time ts2)))
+		day1 (time-to-days (org-time-string-to-time
+				    ts1 (current-buffer) pos))
+		day2 (time-to-days (org-time-string-to-time
+				    ts2  (current-buffer) pos)))
 	  (while (< (setq day1 (1+ day1)) day2)
 	    (or (memq day1 dates) (push day1 dates)))))
       (setq dates (sort dates '<))
@@ -4739,7 +4743,8 @@ This function is invoked if `org-agenda-todo-ignore-deadlines',
 	(org-agenda-skip)
 	(if (and (match-end 1)
 		 (not (= d1 (org-time-string-to-absolute
-			     (match-string 1) d1 nil show-all))))
+			     (match-string 1) d1 nil show-all
+			     (current-buffer) b0))))
 	    (throw :skip nil))
 	(if (and e3
 		 (not (org-diary-sexp-entry (buffer-substring b3 e3) "" date)))
@@ -5157,7 +5162,8 @@ See also the user option `org-agenda-clock-consistency-checks'."
 			   (member todo-state
 				    org-agenda-repeating-timestamp-show-all))
 	      d2 (org-time-string-to-absolute
-		  (match-string 1) d1 'past show-all)
+		  (match-string 1) d1 'past show-all
+		  (current-buffer) pos)
 	      diff (- d2 d1)
 	      wdays (if suppress-prewarning
 			(let ((org-deadline-warning-days suppress-prewarning))
@@ -5263,7 +5269,8 @@ FRACTION is what fraction of the head-warning time has passed."
 			   (member todo-state
 				   org-agenda-repeating-timestamp-show-all))
 	      d2 (org-time-string-to-absolute
-		  (match-string 1) d1 'past show-all)
+		  (match-string 1) d1 'past show-all
+		  (current-buffer) pos)
 	      diff (- d2 d1))
 	(setq pastschedp (and todayp (< diff 0)))
 	;; When to show a scheduled item in the calendar:
@@ -5363,8 +5370,8 @@ FRACTION is what fraction of the head-warning time has passed."
 	      (end-time (match-string 2)))
 	  (setq s1 (match-string 1)
 		s2 (match-string 2)
-		d1 (time-to-days (org-time-string-to-time s1))
-		d2 (time-to-days (org-time-string-to-time s2)))
+		d1 (time-to-days (org-time-string-to-time s1 (current-buffer) pos))
+		d2 (time-to-days (org-time-string-to-time s2 (current-buffer) pos)))
 	  (if (and (> (- d0 d1) -1) (> (- d2 d0) -1))
 	      ;; Only allow days between the limits, because the normal
 	      ;; date stamps will catch the limits.

lisp/org.el

@@ -15403,12 +15403,19 @@ days in order to avoid rounding problems."
 		      l (push m l)))
     (apply 'format fmt (nreverse l))))
 
-(defun org-time-string-to-time (s)
-  (apply 'encode-time (org-parse-time-string s)))
+(defun org-time-string-to-time (s &optional buffer pos)
+  (condition-case errdata
+      (apply 'encode-time (org-parse-time-string s))
+    (error (error "Bad timestamp `%s'%s\nError was: %s"
+		  s (if (not (and buffer pos))
+			""
+		      (format " at %d in buffer `%s'" pos buffer))
+		  (cdr errdata)))))
+
 (defun org-time-string-to-seconds (s)
   (org-float-time (org-time-string-to-time s)))
 
-(defun org-time-string-to-absolute (s &optional daynr prefer show-all)
+(defun org-time-string-to-absolute (s &optional daynr prefer show-all buffer pos)
   "Convert a time stamp to an absolute day number.
 If there is a specifier for a cyclic time stamp, get the closest date to
 DAYNR.
@@ -15423,7 +15430,14 @@ The variable date is bound by the calendar when this is called."
     (org-closest-date s (if (and (boundp 'daynr) (integerp daynr)) daynr
 			  (time-to-days (current-time))) (match-string 0 s)
 			  prefer show-all))
-   (t (time-to-days (apply 'encode-time (org-parse-time-string s))))))
+   (t (time-to-days
+       (condition-case errdata
+	   (apply 'encode-time (org-parse-time-string s))
+	 (error (error "Bad timestamp `%s'%s\nError was: %s"
+		       s (if (not (and buffer pos))
+			     ""
+			   (format " at %d in buffer `%s'" pos buffer))
+		       (cdr errdata))))))))
 
 (defun org-days-to-iso-week (days)
   "Return the iso week number."