org-advertized-archive-subtree: Symbol's function definition is void: org-datetree-find-year-create

[Urs Rau <urs.rau@uk.om.org>]

I am trying to archive completed tasks to a datetree. I am using "Move
Subtree to Archive file" (C-c C-x -C-s) And I get the following error:

release_7.4-419-g68114f
Org-mode version 7.4 (release_7.4.419.g68114f)
afile=/Users/ursr/org/tasksnotes.org_archive
org-advertized-archive-subtree: Symbol's function definition is void:
org-datetree-find-year-create

And I had done a C-c C-x ! to reload all org files, jsut in case. ;-)

I have added the following settings taken from the worg site page:
http://orgmode.org/worg/org-hacks.html

Topic: Archive in a date tree
Posted to Org-mode mailing list by Osamu Okano

(setq org-archive-location "%s_archive::date-tree")
(defadvice org-archive-subtree
  (around org-archive-subtree-to-data-tree activate)
  "org-archive-subtree to date-tree"
  (if
      (string= "date-tree"
               (org-extract-archive-heading
                (org-get-local-archive-location)))
      (let* ((dct (decode-time (org-current-time)))
             (y (nth 5 dct))
             (m (nth 4 dct))
             (d (nth 3 dct))
             (this-buffer (current-buffer))
             (location (org-get-local-archive-location))
             (afile (org-extract-archive-file location))
             (org-archive-location
              (format "%s::*** %04d-%02d-%02d %s" afile y m d
                      (format-time-string "%A" (encode-time 0 0 0 d m y)))))
        (message "afile=%s" afile)
        (unless afile
          (error "Invalid `org-archive-location'"))
        (save-excursion
          (switch-to-buffer (find-file-noselect afile))
          (org-datetree-find-year-create y)
          (org-datetree-find-month-create y m)
          (org-datetree-find-day-create y m d)
          (widen)
          (switch-to-buffer this-buffer))
        ad-do-it)
    ad-do-it))
;;

How do I fix this and make sure I can file into a datetree? Also is
this going to be based on USA dates or will it work right with
European dates?

Thanks.

--
Urs Rau