How to do arithmetics when creating a new card

Question

Hi, I want to create a new card using trello's automation feature. The title of this card should be set to "Report ", where should be replaced by the number of weeks that have passed since a certain week (e.g., "Report 17" in week number 22). My current approach is to set the card's title to "Report {weeknumber - 5}". However, the calculation is not evaluated. I did some research that arithmetics are possible for custom number fields. However, I cannot use custom fields. Thanks in advance!

Hannah Humbert - Simpla Workflows · Answer

@Sebastian Duda it is possible to calculate the number of days, weeks, etc. between two dates in Trello, but it is a bit complex. You'll need to convert the dates to epoch so they become numerical fields. Here's an example:

when a card is added to list "Completed", set date custom field "Completion Date" to now, set custom field "Days" to "({{%Completion Date}~X} - {{%Start Date}~X}) / 86400"

Can you share the full automation you want to accomplish including the trigger?

Lara · Answer

Hi Sebastian,

Thanks for reaching out!

To perform the calculation for the current week number, minus 5 weeks, you'll need to format the variable like so:

Report {weeknumber-5w}

You can read more about arithmetic and formatting in date variables here: https://support.atlassian.com/trello/docs/arithmetic-and-formatting-in-date-variables/

Let me know how that goes,

Lara
The Trello Team

Sebastian Duda · Answer

Technically, I'm looking for a way to calculate something like "Report ". However, this seems too complex. Thus, my idea was to refactor it and do a simple subtraction, i.e., "Report ". However, the arithmetics are not evaluated in the title and I don't understand why.