Mine is this based on Jethro’s suggestion, and works perfectly in my markdown files (it should work on any other text file types, like org)
(add-hook 'after-init-hook
(lambda ()
(my/load-md-roam)
;; time stamp
(setq time-stamp-start "modified:[ ]+\\\\?")
(setq time-stamp-end "$")
(setq time-stamp-format "%Y-%m-%dT%H%M%S")
(add-hook 'before-save-hook #'time-stamp)))
For where you can see the recommendation not to change the variable:
The documentation of the variable time-stamp-pattern – you should be able to view it via C-h v (describe-variable)
