(defun collect-basenames (dir pattern)
  (mapcar #'file-name-base
          (directory-files-recursively dir pattern)))
(ignore-errors
(let* ((org-dir (file-name-directory (or load-file-name buffer-file-name)))
       (org-files (collect-basenames org-dir "\\.org$"))
       (html-dir (concat (file-name-as-directory user-emacs-directory) (file-name-as-directory "pages")))
       (html-files (collect-basenames html-dir "\\.html$")))
       (if (not (equal org-files html-files)) ; each org file is an html page
         (let* ((html-file (concat html-dir "site_map.html"))
               (html-ts (file-attribute-modification-time (file-attributes html-file)))
               (org-html-file (concat org-dir "site_map.html"))
               (org-html-ts (file-attribute-modification-time (file-attributes org-html-file))))
               (if (or (time-less-p org-html-ts html-ts) (time-equal-p org-html-ts html-ts))
                 (progn
                   (message "setting %s timestamp to %s's +1s" org-html-file html-file)
                   (set-file-times org-html-file (time-add html-ts (seconds-to-time 1))))
                 (message "skipping timestamp update for site_map %s as it is already more recent than %s" org-html-file html-file)))))
)