CultureInfo.DateTimeFormat.FirstDayOfWeek not changing results for CultureInfo.Calendar.GetDayOfWeek(DateTime);

Question

I need to create a billing scheme where to pay week goes Friday to Thursday.  
CultureInfo cult = new CultureInfo("en-US",true);
Calendar FIMCal;
cult.DateTimeFormat.FirstDayOfWeek = DayOfWeek.Friday;
cult.DateTimeFormat.CalendarWeekRule = CalendarWeekRule.FirstFullWeek;

FIMCal = cult.Calendar;
int result = (int)FIMCal.GetDayOfWeek(DateTime.Now);
The variable "result" is assigned 1 for Monday when it should be 3. Friday should be 0 Thurday 6 and so on.
Why is the Cultureinfo not changing the DayofWeek enum???