{
 Data sometimes have to be filtered regarding to working
 days (Mo.-Fri.) of the current Week. Following procs set
 your TDateTimePicker automatically.
}

function GetMonday(RefDay: TDate): TDate;
var
 DoW: Integer;
 DateOffset: Integer;
begin
 DoW := DayOfWeek(RefDay);
 // Montag der Woche
 if DoW = 1 then DateOffset := -6
 else
  DateOffset := Dow - 2;
 Result := RefDay - DateOffset;
end;
function GetFriday(RefDay: TDate): TDate;
var
 DoW: Integer;
 DateOffset: Integer;
begin
 DoW := DayOfWeek(RefDay);
  {
  Friday of current week
  Freitag der Woche
  }
 if DoW = 1 then DateOffset := -2
 else
  DateOffset := Dow - 6;
 Result := RefDay - DateOffset;
end;
procedure SetWorkingDaysFilter(S, E: TDateTimePicker);
var
 N: TDate;
begin
 N := Now;
 S.Date := GetMonday(N);
 E.Date := GetFriday(N);
end;
{Just as short as simple}
{Einfach und kurz}

type
 TForm1 = class(TForm)
  DStart: TDateTimePicker;
  DEnd: TDateTimePicker;
  btSetFilter: TButton;
  procedure btSetFilterClick(Sender: TObject);
 end;
procedure TForm1.btSetFilterClick(Sender: TObject);
begin
 SetWorkingDaysFilter(DStart, DEnd);
end;