Add timestamp selector.

README.org

@@ -192,6 +192,7 @@ These selectors take one argument alone, or multiple arguments in a list.
 +  =:children= :: Select any item that has child entries.  Argument may be ~t~ to match if it has any children, ~nil~ to match if it has no children, ~todo~ to match if it has children with any to-do keywords, or a string to match if it has children with certain to-do keywords.  You might use this to select items that are project top-level headings.  Be aware that this may be very slow in non-daily/weekly agenda views because of its recursive nature.
 +  =:date= :: Group items that have a date associated. Argument can be =t= to match items with any date, =nil= to match items without a date, or =today= to match items with today’s date. The =ts-date= text-property is matched against.
 +  =:deadline= :: Group items that have a deadline. Argument can be ~t~ (to match items with any deadline), ~nil~ (to match items that have no deadline), ~past~ (to match items with a deadline in the past), ~today~ (to match items whose deadline is today), or ~future~ (to match items with a deadline in the future). Argument may also be given like ~before DATE~ or ~after DATE~ where DATE is a date string that ~org-time-string-to-absolute~ can process.
++  =:timestamp= :: Group items whose bodies contain an active timestamp.  Argument can be ~t~ (to match items with any timestamp), ~past~ (to match items with timestamps in the past), ~today~ (to match items with timestamps set to today), or ~future~ (to match items with timestamps in the future).  Argument may also be given like ~before DATE~ or ~after DATE~, where DATE is a date string that ~org-time-string-to-absolute~ can process.
 +  =:effort<= :: Group items that are less than (or equal to) the given effort. Argument is a time-duration string, like ~5~ or ~0:05~ for 5 minutes.
 +  =:effort>= :: Group items that are higher than (or equal to) the given effort. Argument is a time-duration string, like ~5~ or ~0:05~ for 5 minutes.
 +  ~:file-path~ :: Group items whose buffers' filename paths match any of the given regular expressions.

org-super-agenda.el

@@ -368,6 +368,7 @@ returned by :SECTION-NAME as the first item, a list of items not
 matching the :TEST as the second, and a list of items matching as
 the third."
   (declare (indent defun)
+           (doc-string 2)
            (debug (&define symbolp stringp
                            &rest [&or [":section-name" [&or stringp def-form]]
                                       [":test" def-form]
@@ -470,7 +471,7 @@ DATE', where DATE is a date string that
 (org-super-agenda--defgroup scheduled
   "Group items that are scheduled.
 Argument can be `t' (to match items scheduled for any date),
-`nil' (to match items that are not schedule), `past` (to match
+`nil' (to match items that are not scheduled), `past' (to match
 items scheduled for the past), `today' (to match items scheduled
 for today), or `future' (to match items scheduled for the
 future).  Argument may also be given like `before DATE' or `after
@@ -504,10 +505,50 @@ DATE', where DATE is a date string that
                                        ((or 'before 'on 'after) target-date))))
                    (org-super-agenda--compare-dates comparison entry-time compare-date))))))))
 
+(org-super-agenda--defgroup timestamp
+  "Group items whose bodies contain an active timestamp.
+Argument can be `t' (to match items with any timestamps),
+`past' (to match items with timestamps in the past), `today' (to
+match items with timestamps set to today), or `future' (to match
+items with timestamps in the future).  Argument may also be given
+like `before DATE' or `after DATE', where DATE is a date string
+that `org-time-string-to-absolute' can process."
+  :section-name (pcase (car args)
+                  ('t "Active timestamps")
+                  ('today "Active timestamps for today")
+                  ('future "Future active timestamps")
+                  ('past "Past active timestamps")
+                  ('before (concat "Active timestamps before " (cadr args)))
+                  ('on (concat "Active timestamps on " (cadr args)))
+                  ('after (concat "Active timestamps after " (cadr args))))
+  :let* ((target-date (pcase (car args)
+                        ((or 'before 'on 'after)
+                         (org-time-string-to-absolute (org-read-date nil nil (cadr args))))))
+         (comparison (car args))
+         (compare-date
+          (pcase comparison
+            ((or 'future 'past 'today) (org-today))
+            ((or 'before 'after 'on) target-date)
+            (other
+             (message "CMP = %s => nil" other)
+             nil))))
+  :test (org-super-agenda--when-with-marker-buffer (org-super-agenda--get-marker item)
+          (let ((limit (org-entry-end-position)))
+            (cl-macrolet
+                ((next-timestamp
+                  ()
+                  `(when (re-search-forward org-ts-regexp limit :no-error)
+                     (org-time-string-to-absolute (org-read-date nil nil (match-string 1))))))
+              (cl-loop for next-ts = (next-timestamp)
+                       while next-ts
+                       thereis (or (eq comparison 't)
+                                   (org-super-agenda--compare-dates comparison next-ts compare-date)))))))
+
 (defun org-super-agenda--compare-dates (comparison date-a date-b)
   "Compare DATE-A and DATE-B according to COMPARISON.
 COMPARISON should be a symbol, one of: `past' or `before',
 `today' or `on', `future' or `after'."
+  (message "CMP %s vs %s" date-a date-b)
   (pcase comparison
     ((or 'past 'before) (< date-a date-b))
     ((or 'today 'on) (= date-a date-b))