Setting a windows batch file variable to the day of the week

Question

I have a windows batch file that runs daily. Wish to log data into a file and want to rotate it (i.e. having at most the last 7 days worth of data).

Looked into the

Answer 1

Rem Remove the end comma and add /A to set for this line worked for me.
set /A a=yy/100, b=a/4, c=2-a+b, e=36525*(yy+4716)/100, f=306*(mm+1)/10