add org macro mdate

settings/org-settings.el

@@ -1160,7 +1160,15 @@ except:
   ;;             'my-org-export-filter-hyphen-shy)
   (setq org-export-with-smart-quotes t)  ;; OPTIONS keyword, e.g., "’:t".
   (setq org-export-with-sub-superscripts '{})  ;; OPTIONS keyword, e.g., "^:{}".
-  
+
+  ;; see also https://orgmode.org/manual/Macro-Replacement.html
+  ;; #+date: {{{mdate(%e %B %Y\, %H:%M)}}}
+  (setq org-export-global-macros
+        '((mdate . "(eval (let ()
+ (setq-local system-time-locale \"en_US.UTF-8\")
+ (format-time-string $1 (file-attribute-modification-time
+  (file-attributes (buffer-file-name))))))")))
+
   ;; http://permalink.gmane.org/gmane.emacs.orgmode/93971
   ;; https://emacs.stackexchange.com/questions/30575/adding-latex-newpage-before-a-heading/30892
   (defun my-org-headline-string-element (headline backend info)