Restore org timestamp hook

config.el

@@ -198,6 +198,33 @@
   (interactive)
   (remove-hook 'before-save-hook #'kernel/md/save-with-timestamp 'local))
 
+(defun kernel/org/save-with-timestamp ()
+  "Save org file with timestamp."
+  (interactive)
+  (save-excursion
+    (goto-char (point-min))
+    (let* ((section-last-update-key-re "^#\\+last_update[ ]*:[ ]*")
+           (section-last-update-key "#+last_update: "))
+      (if (re-search-forward section-last-update-key-re nil t)
+          (kill-line)
+        ;; else
+        (message "No last_update key found.")
+        ;; insert last_update into the first line
+        (goto-char (point-min))
+        (electric-newline-and-maybe-indent)
+        (forward-line -1)
+        (insert section-last-update-key))
+      (kernel/timestamp))))
+
+(defun kernel/org/add-save-with-timestamp-hook ()
+  "Add org timestamp hook."
+  (interactive)
+  (add-hook 'before-save-hook #'kernel/org/save-with-timestamp nil 'local))
+
+(defun kernel/org/delete-save-with-timestamp-hook ()
+  "Delete org timestamp hook."
+  (interactive)
+  (remove-hook 'before-save-hook #'kernel/org/save-with-timestamp 'local))
 
 ;;
 ;; kernel key maps
@@ -318,6 +345,7 @@
 ;;
 (add-hook! 'prog-mode-hook #'copilot-mode)
 (add-hook! 'markdown-mode-hook #'kernel/md/add-save-with-timestamp-hook)
+(add-hook! 'org-mode-hook #'kernel/org/add-save-with-timestamp-hook)
 
 (after! python
   (setq pipenv-projectile-after-switch-function