should it not be something like:

Code:
int numberOfDaysInWeek = 7;
int numberOfDaysInWeekend = 2;

int totalWeekendDays = totalDaysTimeSpan * numberOfDaysInWeekend / numberOfDaysInWeek;
where totalDaysTimeSpan is the endDate - startDate



don't think that'll work as you could be staying for say 4 days, (Thursday - Monday) and it would calculate that as 1, where it should be 2 (sat + sun)