Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

uses
   CommCtrl;

 procedure TForm1.DateTimePicker1DropDown(Sender: TObject);
 var
   wnd: HWND;
   Style: Integer;
 begin
   wnd := DateTime_GetMonthCal(DateTimePicker1.Handle);
   if wnd <> 0 then
   begin
     Style := GetWindowLong(wnd, GWL_STYLE);
     SetWindowLong(wnd, GWL_STYLE, Style or MCS_NOTODAY or MCS_NOTODAYCIRCLE);
   end;
 end;

 { 
  The calendar will still highlite the current day but the circle and the 
  today display at the bottom are gone. 
}