【c++】關於類繼承運算符重載友元函數

/*以下代碼在vc++6.0中通不過
並不意味代碼有誤，請更換編譯
器運行---枯等街寒又何妨2014/01/05*/
#include<iostream>
#include<iomanip>
using namespace std;
class Time
{
public:
    void set_time(int,int,int);
	Time(int y=0,int m=0 ,int d=0 );
    void display(void);
	Time operator++();
	Time operator--(int);
	friend ostream &operator<<(ostream &out,Time &t);
private:
	int year;
	int month;
	int day;
};
class Date:public Time
{
 public:
    Date(int y,int m1,int d,int h,int m2,int s);
    void set_date(int,int,int,int,int,int);   
    void display(void); 
    
 private:
   int hour;
   int minute;
   int second;
};
Time::Time(int y,int m,int d) //構造函數
{
  set_time(y,m,d);
}
 
void Time::set_time(int y,int m,int d)  //成員函數
{
  year=y;
  month=m;
  day=d;
}

void Time ::display(void)
{
  cout<<"year:"<<setfill('0')<<setw(4)<<year;
  cout<<"\tmonth:"<<setw(2)<<setfill('0')<<month;
  cout<<"\tday:"<<setw(2)<<setfill('0')<<day<<endl;
}
Time Time::operator++()    //重載++前置運算符
{
 return Time(year,month,++day); //注意不要寫成day+1,因爲這樣不會改
                                //變day的值,Time的值不會發生任何的變化
}

Time Time::operator --(int) //重載--後置運算符
{
  Time temp(*this);
  day--;
  return temp;
}

ostream& operator<<(ostream &out,Time &t)
{
 out<<"year:"<<t.year<<"\tmonth:"<<t.month<<"\tday:"<<t.day<<endl;
 return out;
}

Date::Date(int y,int m1,int d,int h,int m2,int s):Time(y,m1,d)
{
  hour=h;
  minute=m2;
  second=s;              
}

void Date::set_date(int y,int m1,int d,int h,int m2,int s)
{
 Time::set_time(y,m1,d);
 hour=h;
 minute=m2;
 second=s;     
}

void Date::display(void )
{
 Time::display();
 cout<<"hour:"<<setw(2)<<setfill('0')<<hour;
 cout<<"\tminute:"<<setw(2)<<setfill('0')<<minute;
 cout<<"\tsecond:"<<setw(2)<<setfill('0')<<second<<endl;     
} 

 int main()
 {
 Time time_1(2014,1,5), time_2;
 time_2.set_time(1900,1,1);
 time_1.display();
 time_2.display();
 ++time_1;//等價於time_1.operator++();
 time_1.display();
 (time_1--).display();
 time_1.display();
 cout<<time_1;
 Date date1(2014,1,5,19,16,10),date2;
 date1.display();
 system("pause");
 return 1;
 }