C :

#include<stdio.h> 
int main(int argc,char* argv[])
{
	int day1,hour1,minutes1;
	int day2,hour2,minutes2;
	int temphour,tempday;
	scanf("%d%d%d%d%d%d",&day1,&hour1,&minutes1,&day2,&hour2,&minutes2);
	day1+=day2;
	hour1+=hour2;
	minutes1+=minutes2;
	if(minutes1>60)
	{
		temphour=minutes1/60;
		hour1+=temphour;
		minutes1=minutes1-temphour*60;
	}
	if(hour1>24)
	{
		tempday = hour1/24;
		day1+=tempday;
		hour1=hour1 - tempday*24;
	}
	printf("%d\n%d\n%d",day1,hour1,minutes1);
	return 0;
} 

C++ :

#include<iostream>

using namespace std;

void TimeAdd(int&, int&, int&,int&,int&,int&);

int main()
{
	int days, hours, minutes,x,y,z;
	cin >> days >> hours >> minutes;
	while (cin)
	{
		TimeAdd(days, hours, minutes, x, y, z);
		cout << days << endl << hours << endl << minutes << endl;
		cin >> days >> hours >> minutes;
	}
	return 0;
}

void TimeAdd(int&a, int&b, int&c, int& x, int& y, int& z)
{
	int m = 0;
	int n = 0;
	cin >> x >> y >> z;
	c += z;
	while (c > 59)
	{
		c -= 60;
		m++;
	}
	b = b + y + m;
	while (b > 23)
	{
		b -= 24;
		n++;
	}
	a = a + x + n;
}