The following will work:

    # Local Variables:
    # org-time-stamp-custom-formats: ("<%Y-%m>" . "<%Y-%m %H:%M>")
    # eval: (org-toggle-time-stamp-overlays)
    # End:

Using `(org-toggle-time-stamp-overlays)` (<kbd>C-c</kbd><kbd>C-x</kbd><kbd>C-t</kbd>) to ensure they are properly displayed.

You will need to confirm that these are safe local variables for them to apply however once they are approved the document will load with them already showing.

Toggle command referenced from the [Org Manual](


Showing differences between the various local variable settings

The three pictures below show:

  1. Answer as above
  2. Answer without including the `eval` line.  This does not show the custom timestamps.  <kbd>C-c</kbd><kbd>C-x</kbd><kbd>C-t</kbd> will toggle them to be visible
  3. Incomplete `org-time-stamp-custom-formats` specification.  If custom timestamps are toggled the timestamps are no longer fontified.  They will show properly once custom timestamp overlays are removed.

![Various Local Variable Settings][1]