It helped me too...here is my code with concrete paths...very thanks
@Echo off
echo.Backing up database...
set dd=%Date:~0,2%
set mm=%Date:~3,2%
set yy=%Date:~6,4%
set ddy=%Date:~0,2%
set mmy=%Date:~3,2%
set yyy=%Date:~6,4%
set /A ddy -= 1
if %ddy%==0 set /A mmy-=1
if %mmy%==0 (
set mmy=12...