How to set a due date on a card based on due date on another card

Question

Hello there,

I'm trying to automate my data input in Butler by creating a Rule, but it's not going my way.

Intention: I have four lists - Stages 1-4. Each of the stages has cards that are responsible for setting up the event, for example, Stage 1 is Set-Up (includes cards such as Send Calendar Invites, etc), and Stage 4 is Launch (cards such as Launch Event, etc). How can I automate my Trello Board so that when I fill in the due date on the "Send Calendar Invites" card in Stage 1, the cards in Stage 2,3,4 are automatically filled up according to the number of days programmed in the automation, for example, the date in Stage 4 on the card "Launch Event" will be set to three weeks after the date set in "Send Calendar Invites".

My solution: when a due date is set on a card with a name containing "Send Calendar Invites", find a card titled "Launch Event" in the list "Stage 4 - Launch", set due date in 1 month at 12:00 pm.

Problem: The problem is that on the "Launch Event Card", the due date will be set to one month from today - i.e.:
If today (30/03/23) the "Send Calendar Invites" card due date is set to 01/05/23 and the above automation is used, the "Launch Event" card will set the Due Date to 30/04/23 instead of 01/06/23.

Does anyone have an idea how this can be solved?
I hope what I write makes sense, if not, please let me know and I'll try to explain it better.

Vongsawat · Answer

So the difficult bit here is that setting due dates are very limited. You can't just set it to a variable or whatnot.

Option 1 is to set it via custom field. Provided you're on the paid plan, this has a built-in solution.

Option 2 is actually in the Triggers and uses the workaround in that dates put in to the name of a card, can automatically be turned in to a due date (and the text summarily removed)

In both cases, you'd have to set the custom field or card name to be/include {triggercardduedate+1m} for instance. Guide to applying arithmetic to dates.

Mike - Dreamsuite Consulting · Answer

Custom field can help here.  Have a date custom field and then do:

Command 1

"When a due date is set on a card with a name containing "...", find a card and set the custom field "Date" to {triggercardduedate}"

Command 2

"when the custom field "Date" is set on a card in the list "Stage 4", set the due date to {customfieldvalue+1m}