add calculated field weeknumber

Hi,

I'm trying to add in meetings the weeknumber and monthnumber.

In the reporting we want to group the meetingscount by month and by week.

Currenlty we only get the group by option from Sugar, this will add them as W01 2019, W01 2020 (seperate columns).

What I would like to do is set them as W01, second level 2019 | 2020 .

Anybody any idea what calculation I can use?

Thank you in advance.