Convert date to week number starting with a specific date

I have a field called “Campaign Date” in my database where I start my experiment (November 1st). I would like to create a field where my first week of experiments is labeled Week 1, and so on.

Can someone point me in the right direction?

Hello Maya
I’m not sure I understand what you want
But if you want to return the week number of a date (eg : fieldname = “Campaign Date”) based on the first of november 2021, you can add a formula field: “Campaign Week”
1+DATETIME_DIFF(
{Campaign Date},
DATETIME_PARSE(“11/01/2021”,“MM/DD/YYYY”),
‘w’
)

You add 1 so that first week is 1 , not 0