Weeknumber for sundays


Do you know if we can have the following use case :
I have a date and the week number with a formula.
I would like that for example Sunday 5 of december is week 49 and not 50, because in my work and in our calendars weeks start the monday and end the sunday.
So here when I want to follow the work for a specific week, I have all the days excepted the sunday that is counted the week after.

Does it makes sense to you ?

Thank you for your help,


Hello again,

For information it seems to work well with ISOWEEKNUM formula,

The sunday is in the good week number,