[pesi]

Код:

var
  MousePosition: TPoint;
  CalendarPosition: TPoint;
begin
  MousePosition := Mouse.CursorPos;
  CalendarPosition := (Sender as TControl).ClientOrigin;
  if (MousePosition.Y > CalendarPosition.Y + GetSystemMetrics(SM_CYICON)) then
   Edit1.Text:=DateToStr(MonthCalendar1.Date);
end;