Классы: Разность дат С++

#include <cstdlib>
#include <iostream>
#include <windows.h>
 
 
using namespace std;
 
 
int main(int argc, char *argv[])
{
    int day,month,year,day1,month1,year1;/*dannye nachala/konca otscheta*/
    int god[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
 
/*vood dannyh*/ 
 
/*nachal'nye den'/mesyac/god*/
 
    cout << "in\nday:";
    cin >>  day;
    cout << "month:";
    cin >> month;
    cout << "year:";
    cin >> year;
    
/*konechnye den'/mesyac/god*/
    
    cout << "out\nday:";
    cin >> day1;
    cout << "month:";
    cin >> month1;
    cout << "year:";
    cin >> year1;
    
/*podschet dney*/   
 
    int summa = 0;/*obschaya summa dney*/
 
/*podschet dney v nachal'nom gode*/ 
 
    for (int i = month; i <=11; i++)
        summa = summa + god[i];
    
    if (year%4 == 0) /*proverka na vysokosnost' nachal'nogo goda*/
        summa++;
 
    summa = summa - day;
    
/*podschet dney m konechnom gode*/
    
    for (int i = 0; i < month1; i++)
            summa = summa + god[i];
            
    if (year1%4 == 0) /*proverka na vysokosnost' konechnogo goda*/
        summa++;
    
    summa = summa + day1;
    
/*vycheslenie kolichestva dney mejdu nachal'nym i konechnym godom*/ 
 
    if (year1 - year > 1)
    {
        int raznica = year; /*raznica mejdu nachal'nym i konechnym godom*/
        
        for(int i = 1; i < year1 - year; i++)
        {
            raznica = raznica + 1;
            
            for(int j = 0; j <= 11; j++)
                summa = summa + god[j];
                
            if (raznica%4 == 0) /*proverka na vysokosnost'*/
                summa++;
        }
    }
    
    cout << summa << "\n";
 
    system("PAUSE");
    return EXIT_SUCCESS;
}