Среднее значение, оператор перегрузки

#include <iostream>
#include <iomanip>
using namespace std;
const int LEN = 20;
 
class ZNAK
{
private:
    char name[LEN];
    char surname[LEN];
    int z, ost;
public:
    int bday[3];
    int god=2021;
    void getdata()
    {
        cout << "\n Vvedite imya: " ; cin >> name;
        
        cout << " Vvedite familiyu: " ; cin >> surname;
        
        cout << " Vvedite god rojdeniya: " ; cin >> bday[0];
        
        cout << " Vvedite mesyac rojdeniya: " ; cin >> bday[1];
        
        cout << " Vvedite chislo rojdeniya: " ; cin >> bday[2];
    }
    void computation()
    {
        if (bday[1]=1 && bday[2]<20)
        {   god=god++;  }
        else
        {   god=god;    }
    }   
    void putdata()
    {
        cout << "\n Imya: " << name;
        cout << "\n Familiya: " << surname;
    }
};
 
class ZNAK2 : public ZNAK
{
private:
    int h, m ;
public:
    void getdata()
    {
        cout << "\n Vvedite vremya rojdeniya: " ;
        cout << "\n Chasi (00-23): " ; cin >> h ;
        cout << " Minuti (00-59): " ; cin >> m ;
    }
    
    void putdata()
    {
        cout << " Vremya rojdeniya - "; 
        cout << setfill('0') << setw(2) << h << ":" << setw(2) << m ;
    }
 
};
 
class ZNAK3 : public ZNAK
{
private:
    char city[LEN];
public:
    void getdata()
    {
        cout << "\n Vvedite naselenniy punkt, gde rodilis: " ; cin >> city;
    }
    void putdata()
    {
        cout << " Naselenniy punkt, gde rodilis: " << city;
    }
};
 
int operator^(const ZNAK &z11, const ZNAK &z21)
    {
        return ((god-z11.bday[0]+god-z21.bday[0])/ 2);
    }
 
int main ()
{
    ZNAK z11, z21;
    ZNAK2 z12, z22;
    ZNAK3 z13, z23;
    
    cout << "\nVvod 1:"; z11.getdata();
    cout << "\n"; z12.getdata();
    cout << "\n"; z13.getdata();
    
    cout << "\nVvod 2:"; z21.getdata();
    cout << "\n"; z22.getdata();
    cout << "\n"; z23.getdata();
    
    cout << "\nInfo"; z11.putdata();
    cout << "\n"; z12.putdata();
    cout << "\n"; z13.putdata();
    
    cout << "\nInfo2"; z21.putdata();
    cout << "\n"; z22.putdata();
    cout << "\n"; z23.putdata();
    
    cout << "\nAVG vozrast: ";
    cout << (z11^z21);
};

int operator^(const ZNAK &z11, const ZNAK &z21)
{
    return ((z11.god-z11.bday[0]+z21.god-z21.bday[0])/ 2);
}

    void computation()
    {
    if (bday[1]=1 && bday[2]<20)
        {   god=god++;  }
    else
        {   god=god;    }
    }

bday[1]=1

bday[1]==1

#include <iostream>
 
struct Birthday {
    unsigned year;
    unsigned month;
    unsigned day;
 
    unsigned getAdjustedAgeInYears(std::size_t toYear) const {
        return toYear - year + (month == 1 && day < 20 ? 1 : 0);
    }
};
 
std::ostream &operator<<(std::ostream &out, const Birthday &b) {
    return out
        << (b.day < 10 ? "0" : "" ) << b.day << "."
        << (b.month < 10 ? "0" : "" ) << b.month << "."
        << b.year;
}
 
std::istream &operator>>(std::istream &in, Birthday &b) {
    return in >> b.day >> b.month >> b.year;
}
 
int main() {
    Birthday a{}, b{};
    std::cin >> a >> b;
    std::cout << a << std::endl << b << std::endl;
    double averageAge = (a.getAdjustedAgeInYears(2022) + b.getAdjustedAgeInYears(2022)) / 2.0;
    std::cout << "Average age is: " << averageAge;
    return 0;
}

using namespace std;