can we assign member variable of one class to function definition of another class?

#include<iostream.h>
#include<conio.h>
class time24;
class time12
{
	int hour,minute,second;
	char *meridian;
	public:
	void getdata();
	void putdata();
	void summation(time24 x);
};
class time24
{
	int hour,minute,second;
	public:
	void getdata();
	void conto12();
	friend void time12::summation(time24 x);
};

void time12::summation(time24 x)
{
	hour=hour+x.hour;
	minute=minute+x.minute;
	second=second+x.second;
	meridian="PM";
	if(second>=60)
	{
		minute=minute+(second/60);
		second=second%60;

	}
	if(minute>=60)
	{
		hour=hour+(minute/60);
		minute=minute%60;

	}
	x.conto12();

}
void time24::conto12()
{

	if(hour>12)
	{
	       hour=hour-12;
	       meridian="AM";
	}
}

void time12::getdata()
{
	cout<<"\nenter hour:";
	cin>>hour;
	cout<<"enter minute:";
	cin>>minute;
	cout<<"enter second:";
	cin>>second;
}
void time24::getdata()
{
	cout<<"\nenter hour:";
	cin>>hour;
	cout<<"enter minute:";
	cin>>minute;
	cout<<"enter second:";
	cin>>second;
}
void time12::putdata()
{
	cout<<"time:"<<hour<<":"<<minute<<":"<<second<<" "<<meridian;
}
void main()
{
	clrscr();
	time12 a;
	time24 b;
	a.getdata();
	b.getdata();
	a.summation(b);
	a.putdata();
	getch();
}