Actually this not related to fullcalendar but I think this script will help you for getting bussiness/Active days (excluding weekends) from given month and year.
function getActiveDays(month,year){
var daysinmonth=Date.getDaysInMonth(year,month);
var sundays=0;
for(i=1;i<=daysinmonth;i++){
var dayname = new Date(year,month,i).getDayName();
if(dayname=="Sunday") {
sundays++;
};
}
activedays=daysinmonth-sundays;
return activedays;
}
the function above will eliminate sundays from days of the month. for example :
getActiveDays(7,2012)
will return 27 active days (from august, 2012).
This function use date.js library