I've been trying to get a due date set from card description by pulling the {datenumber} or {isodate} as the content of the card is being emailed to Trello.
I know this was a past feature of Butler because I have another board where a rule that I wrote works just fine, but I cannot edit that rule to work correctly on this new board. I've tried setting custom fields using wildcards and follow up actions to no avail.
It's key to have the due date for getting details of the card in the calendar view and I prefer to not manually enter every single instance that comes in.