Since 6.6 SP1, we’ve added a checkbox to make it possible to exclude weekend days from the Date Selector when:
1) Running a financial report from the ToolBox/Objects or the Objects Tree. 
2) From the 'Financial Lines In Range' Date Selector in the Financial Reports window.
Note that it does NOT exclude Public Holidays, it is ONLY weekends.
This is useful if you sometime book projects on weekends. But when you run Financial Reports on utilisation/profit over a period of time (from selected Start/End dates) farmerswife will include the weekend days in the "Selected Days In Range", which causes the utilisation/profit to be lower. To avoid this, you can tick the new box to "Exclude Weekends".
Note that the bookings on the weekend will also be excluded from the report.