7週目タスク1エラー

#include<iostream>

using namespace std;
class Time
{
public:
	Time(int=0,int=0,int=0);
	void show_time( ); //  is_24 from0，      -20:23:5/8:23:5 pm/08:23:05 pm
	void add_seconds(int); //  n  
	void add_minutes(int); //  n    
	void add_hours(int); //  n    
	static void change24();  //      is_24， 12 24      
	static void changefrom0();   //      from0，      0
private:
	static bool is_24; // true ，24   ， 20:23:5； flase，12   ，   8:23:5 pm 
	static bool from0; // true ，  0，8:23:5   08:23:05
	int hour;
	int minute;
	int sec;
};
Time::Time(int a ,int b ,int c)
{
	hour = a ;
	minute = b; 
	sec = c; 
}

bool Time::is_24 = false  ;
bool Time::from0 = false ;
void Time::change24()
{
	 if(is_24 == true)
     	  is_24 = false;
	 else
		  is_24 = true;
}
void Time::changefrom0()
{
	if(from0 == true)
		from0 = false;
	else
		from0 = true;
}
void Time::add_seconds(int n)
{
    sec = sec + n;
	while(sec >= 60)
	{
		sec = sec - 60;
		minute ++;
	}
}
void Time::add_minutes(int n)
{
    minute = minute + n;
	while(minute >= 60)
	{
		minute = minute - 60;
		hour ++;
	}
}
void Time::add_hours(int n)
{
    hour = hour + n;
	while(hour >= 24)
	{
		hour = hour - 24;
	}
}
void Time::show_time( )
{
	if(is_24)
	{
		if (hour > 12)
			hour = hour - 12;
	    if(from0)
	     {
		    if(hour < 10)
			     cout << "0";
		    cout << hour <<":" ;
		    if(minute < 10)
			     cout << "0"; 
		    cout << minute<< ":"  ;
		    if (sec < 10)
			     cout << "0";
	         cout << sec;
         }
		else 
	      cout << hour << ":" << minute << ":" << sec <<endl;
	}
	else 
	{
		if(from0)
	     {
		    if(hour < 10)
			     cout << "0";
		    cout << hour <<":" ;
		    if(minute < 10)
			     cout << "0"; 
		    cout << minute<< ":"  ;
		    if (sec < 10)
			     cout << "0";
	         cout << sec;
         }
		else 
	       cout << hour << ":" << minute << ":" << sec <<endl ;
	}

}
int main( )   
{
	Time t1(23,14,25),t2(8,45,6); 
	cout<<"24  ,    0："<<endl ;
	cout<<"t1 ："<<endl ;
	t1.show_time();
	cout<<"t2 ："<<endl ;
	t2.show_time();
	t1.add_hours(10);
	t2.add_hours(10);
	Time::changefrom0(); //               

	cout<<endl <<"10   ,       0："<<endl;
	cout<<"t1 ："<<endl ;
	t1.show_time();
	cout<<endl <<"t2 ："<<endl ;
	t2.show_time();
	t1.change24();                    
	cout<<endl<<endl  <<"     ："<<endl;
	cout<<"t1 ："<<endl ;
	t1.show_time();
	cout<<endl <<"t2 ："<<endl ;
	t2.show_time();
	system("pause");
	return 0;
}
    ：showtime     ，   am pm    ，   ，    .....