如何编写date类和person类

编写能创建具有生日（Date）的Person类，可通过构造函数（包括拷贝构造函数）初始化生日，显示打印人的生日，并设置static成员变量来记录Person类有多少个对象，通过static成员函数返回该变量值
date和person类要有无参构造函数和带参构造函数等

#include <iostream>
#include <iomanip>
using namespace std;

class Date
{
public:
    int year;
    int month;
    int day;

    Date() : year(0), month(0), day(0) {}
    Date(int y, int m, int d) : year(y), month(m), day(d) {}
    Date(const Date &d)
    {
        year = d.year;
        month = d.month;
        day = d.day;
    }
    Date &operator=(const Date &d)
    {
        year = d.year;
        month = d.month;
        day = d.day;
    }
    friend ostream &operator<<(ostream &os, const Date &d)
    {
        cout.fill('0');
        os << setw(4) << d.year << ":" << setw(2) << d.month << ":" << setw(2) << d.day << endl;
    }
};

class Person
{
    static int s_count;

public:
    Date birth;
    Person()
    {
        birth = Date();
        s_count++;
    }
    Person(int y, int m, int d)
    {
        birth = Date(y, m, d);
        s_count++;
    }
    Person(const Person &p)
    {
        birth = p.birth;
        s_count++;
    }
    ~Person() { s_count--; }

    static int Count() { return s_count; }
};

int Person::s_count = 0;

int main()
{
    Person a;               //无参构造
    cout << "Birth: " << a.birth;
    cout << "Person: " << Person::Count() << endl;
    Person b(2077, 2, 3);   //带参构造
    cout << "Birth: " << b.birth;
    cout << "Person: " << Person::Count() << endl;
    {
        Person c(b);        //拷贝构造
        cout << "Birth: " << c.birth;
        cout << "Person: " << Person::Count() << endl;
    }
    cout << "After ~Person():" << Person::Count() << endl;
    return 0;
}
// 输出：
// Birth: 0000:00:00
// Person: 1
// Birth: 2077:02:03
// Person: 2
// Birth: 2077:02:03
// Person: 3
// After ~Person():2