Also do not hardcode the parameters like 6 here. There are tons of ways to make it dynamic esp using FIND function.
If you really need the Number only in Weeks then try and break the formula into multiple pieces/Line items. You will surely see a performance gain overall. Let's not neglect these small things, it takes a toll on model performance when the model scales up. Stick to Basics, take one function at a time in system modules.
Step 1 : Create a System Module with 1 line item to manually enter the Calendar year's Starting date.
Eg; 29th December 2019 as First Staring day for calendar year 2020
in Your Main Module create 4 Line items.
Formulas are :
Today's Date : Manually enter the date, which you have to calculate the week for.
Total Days : 'Today''s Date' - System Module.First Week Starting Date (To Calculate number of days between Today's Date and Year Starting Date)
Remainder : MOD(Total Days, 7)
Week Number : IF Total Days = 0 AND Remainder = 0 THEN 1 ELSE IF Total Days < 7 AND Remainder < 7 THEN 1 ELSE IF Total Days >= 7 AND Remainder <> 6 THEN ROUND(Total Days / 7, 0, DOWN)+ 1 ELSE ROUND(Total Days / 7)