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# Lots of questions about dates

Chrystal McFarland January 22, 2023

I've put together a board to track my reading list for 2023, which is a really big step up from the spreadsheets I've used in the past, however, there's one thing I could do fairly easily on a spreadsheet that I can't seem to find the right way to ask the right questions to set this up on Trello.

I'll set a "due date" for my book. Sometimes this is an *actual* due date (like when I'm checking out a book from the library), but most of the time it's just the end of the month or year. There's already a field for this, moving on.

I've created a field for the page numbers/minutes of the book. (I count audiobooks as part of this, btw).

What I can do with the spreadsheet fairly easily is something that looks like this:

`(Number of total [pages OR minutes] - Current location) / (Due date - Today's date)`

What that translates to is, "Take the total number of pages/minutes remaining, divide that by the number of days between now and the due date. The result is the pages/minutes to get through today."

Due dates are set for all of these, but I'm at a loss for how to do the math functions (or if it's even possible). Can someone point me to a reference?

#### 1 accepted

1 vote
Theodoro Reato
Atlassian Team
Atlassian Team members are employees working across the company in a wide variety of roles.
January 24, 2023

Hi Chrystal,

I believe I understood and was able to create this formula, with the help of some awesome teammates :)

You'll need to use Butler to create a Card button that's going to give you the number of pages you need to read to achieve your goals on a Custom Field.

But this command is not basic so bear with me,

You need to have three Custom Fields before the rule, I called them:

• Total number of pages
• Current Location
• Result

##They are all number fields, this is important for our formula :)

The Result is the value we want to achieve, you can follow the instruction in this article to create the Custom Fields on your board: https://support.atlassian.com/trello/docs/using-custom-fields/

On the Automation panel, go to the Card Button page and create a new one:

After it, you'll need to choose a name for your Card Button, go to the Fields tab and use the second option "set custom field _____ to _____"

Choose the Custom field you want to insert the result of the formula, on this case we chose Result and paste the following command on the New Value:

`(({{%Total number of pages}}-{{%Current location}})/({cardduedate~YYMMDD}-{date~YYMMDD}))`

To create this command I used the following articles:

To sum up, to add the value of a Custom Field you need to use {{%___}} and to use a date inside a formula you need to first convert it to a number we made that with the syntax ~YYMMDD, then we used the { } with it as we're obligate while using a variables, and the ( ) to separate the formulas.

After setting the rule you need to have a due date and the Custom Fields Total number of pages and Current location filled out, click on the Butler button and it'll add the results to the Result Custom Field. You'll need to re-click it to update the date if needed.

Chrystal McFarland January 29, 2023

Worked perfectly! Thanks so much!

Theodoro Reato likes this