Everything works in Markdown editor, but when in Rich Text editor :
the Edit / Insert Date menu item is disabled
whatever the shortcut is, you cannot insert the Date (it doesn't insert anything).
Note that it seems to do nothing, but in fact it does change the edition date of the note.
Win 7, 64 bits, 24GB RAM
Joplin 1.3.18 (prod, win32)
Sync Version: 2
Profile Version: 34
BTW, all edition items in the Edit menu are disabled - I don't know if you're aware of this.