gistfile1.txt

(custom-set-variables
  '(org-display-custom-times t)
  '(org-time-stamp-custom-formats (cons (concat "<%Y/%m/%d " (substring (current-time-string) 0 3) ">")
                                        (concat "<%Y/%m/%d " (substring (current-time-string) 0 3) " %H:%M>")))
  )

;;; 訂正版
(custom-set-variables
  '(org-time-stamp-custom-formats (quote ("<%Y/%m/%d %a>" . "<%Y/%m/%d %a %H:%M>")))
  )

;;; とりあえず、動くものにしとく。
(defadvice org-toggle-time-stamp-overlays (around temp-change-around-english-weekday-name)
  (set-locale-environment "C")
  ad-do-it
  (set-locale-environment))
(ad-activate 'org-toggle-time-stamp-overlays)