2-3laboop

#include <iostream>
#include <math.h>
using namespace std;
class Date
{
    int y;     //год
    int m;     //месяц
    int d;     //день
    friend int friend_dec(Date&, Date&);
public:
    Date()//конструктор по умолчанию
    {
        y = 0;
        m = 0;
        d = 0;
    }
    Date(int y_y, int m_m, int d_d)//конструктор по параметрам
    {
        y = y_y;
        m = m_m;
        d = d_d;
    }
    // Конструктор копирования
    Date(const Date& drob) :
        y(drob.y), m(drob.m), d(drob.d)
    {

        cout << "Copy constructor worked here!\n"; // просто, чтобы показать, что это работает
    }
    void set(Date& new_date);
    void get(Date& time);
    void add(Date& time);
};

void Date::get(Date& time)
{
    cout << "Here is your data: ";
    cout << time.d << "." << time.m << "." << time.y << endl;
}
void Date::set(Date& new_date)
{
    int d_in_m[12] = { 31,28,31,30,31,30,31,31,30,31,30,31 };
    int day, month, year, res_d, res_m;
    cout << "Input year: ";
    cin >> year;
    do {
        cout << "Input month: ";
        cin >> month;
        if (month < 1 || month > 12) {
            cout << "Bad months input.Try again.n";
            res_m = 0;
        }
        else res_m = 1;
    } while (res_m == 0);
    do {
        cout << "Input day: ";
        cin >> day;
        if (d_in_m[month - 1] < 1 || day > d_in_m[month - 1]) {
            cout << "Bad days input.Try again.n";
            res_d = 0;
        }
        else res_d = 1;
    } while (res_d == 0);

    new_date.d = day;
    new_date.m = month;
    new_date.y = year;

}
void  Date::add(Date& time)
{
    int day, param, month, year, res_d, res_m;


    cout << "Choose: 1 - add year, 2 - add month, 3 - add day\n";
    cin >> param;
    switch (param)
    {

    case 1:
        cout << "Input year to add: ";
        cin >> year;
        time.y += year;
        break;
    case 2:
        do {
            cout << "Input month to add: ";
            cin >> month;
            if (month < 0) {
                cout << "Bad months input.Try again.\n";
                res_m = 0;
            }
            else res_m = 1;
        } while (res_m == 0);
        if (time.m + month > 12) {
            int dop = 12 - time.m;
            time.y++;
            time.m = 0;
            int ostatok = month % 12 - dop;
            time.m += ostatok;
            int dop_years = month / 12;
            time.y += dop_years;
        }
        else {
            time.m += month;
        }
        break;

    case 3:
        do {
            cout << "Input day: ";
            cin >> day;
            if (day < 0) {
                cout << "Bad days input.Try again.\n";
                res_d = 0;
            }
            else res_d = 1;
        } while (res_d == 0);

        if (day / 365 > 0) time.y += day / 365;
        if (day / 30 > 0)
        {
            time.m += day / 30;
            if (time.m > 12)
            {
                time.y += time.m / 12;
                time.m %= 12;
            }
        }
        else
        {
            time.d += day;
            if (time.d / 30 > 0) time.m++;
        }
        break;

    default: cout << "Bad input.n"; break;
    }

}
int friend_dec(Date& time, Date& new_time)    /*разность дат*/
{
    int d_in_m[12] = { 31,28,31,30,31,30,31,31,30,31,30,31 };
    int days_in_current_months = 0;
    for (int i = 0; i < time.m; i++) days_in_current_months += d_in_m[i];
    days_in_current_months += time.d;
    int gl_time = 365 * time.y + days_in_current_months;
    int days_in_current_new_months = 0;
    for (int i = 0; i < new_time.m; i++) days_in_current_new_months += d_in_m[i];
    days_in_current_new_months += new_time.d;
    int new_gl_time = 365 * new_time.y + days_in_current_new_months;
    return fabs(gl_time - new_gl_time);
}
int main()
{
    Date time;
    time.set(time);
    time.get(time);
    Date new_time;
    new_time.set(new_time);
    new_time.get(new_time);
    cout << "Diferrense in days: " << friend_dec(time, new_time) << endl;
    int i = 0;
    int param;
    cout << "Chose how much ops you want to do: ";
    cin >> param;
    do {
        time.add(time);
        i++;
    } while (i < param);
    time.get(time);
    return 0;
}