function DaysOfMonth(mm, yy: Integer): Integer; 
begin 
  if mm = 2 then  
  begin 
    Result := 28; 
    if IsLeapYear(yy) then Result := 29; 
  end  
  else  
  begin 
    if mm < 8 then  
    begin 
      if (mm mod 2) = 0 then 
        Result := 30 
      else 
        Result := 31; 
    end  
    else  
    begin 
      if (mm mod 2) = 0 then 
        Result := 31 
      else 
        Result := 30; 
    end; 
  end; 
end; 

procedure TForm1.Button1Click(Sender: TObject); 
var 
  days: Integer; 
begin 
  days := DaysOfMonth(7, 2001); 
  ShowMessage('July 2001 has ' + IntToStr(days) + ' days'); 
end;