C++，C++/CX に挑戦！

    #include <ctime>
    time_t time(time_t *timer);

// Date.h
#ifndef ___Class_Date
#define ___Class_Date

#include <string>
#include <iostream>

class Date {
    int y;
    int m;
    int d;

public:
    Date();
    Date(int yy, int mm = 1, int dd = 1);

    int year()  const { return y; }
    int month() const { return m; }
    int day()   const { return d; }
    std::string day_of_week() const;
    Date preceding_day() const;
    std::string to_string() const;
};

std::ostream& operator<<(std::ostream& s, const Date& x);
std::istream& operator>>(std::istream& s, Date& x);

#endif

// Date.cpp
#define _CRT_SECURE_NO_WARNINGS
#include <iomanip>
#include <ctime>
#include <sstream>
#include <iostream>
#include "Date.h"
using namespace std;

Date::Date() {
    time_t current = time(NULL);
    struct tm* local = localtime(&current);
/*
          ↑ tm構造体については、次回《その91》 にチェックする予定です。
*/
    y = local->tm_year + 1900;
    m = local->tm_mon + 1;
    d = local->tm_mday;
}

Date::Date(int yy, int mm, int dd) {
    y = yy;
    m = mm;
    d = dd;
}

string Date::day_of_week() const {
    string dw[] = { "日" ,"月", "火", "水", "木", "金", "土" };
    int yy = y; int mm = m;
    if (mm == 1 || mm == 2) {
        yy--;
        mm += 12;
    }
    return dw[(yy + yy / 4 - yy / 100 + yy / 400 + (13 * mm + 8) / 5 + d) % 7];
}

Date Date::preceding_day() const {
    int dmax[] = { 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 };
    Date temp = *this;

    if (temp.d > 1)
        temp.d--;
    else {
        if (--temp.m < 1) {
            temp.y--;
            temp.m = 12;
        }
        temp.d = dmax[temp.m - 1];
    }
    return temp;
}

string Date::to_string() const {
    ostringstream s;
    s << setfill('0') << y << "年"
      << setw(2)      << m << "月"
      << setw(2)      << d << "日"
      << "(" << day_of_week() << ")";
    return s.str();
}

ostream& operator<<(ostream& s, const Date& x) {
    return s << x.to_string();
}

istream& operator>>(istream& s, Date& x) {
    int y, m, d; char c;
    s >> y >> c >> m >> c >> d;
    x = Date(y, m, d);
    return s;
}

// Human.h
#ifndef ___Class_Human
#define ___Class_Human

#include <string>
#include "Date.h"

class Human {
private:
    std::string name;           // 氏名
    std::string country;        // 国籍
    double height;              // 身長(cm)
    double weight;              // 体重(kg)
    Date birthday;              // 誕生日
public:
    Human(std::string n, std::string c, double h, double w, const Date& bd)
        : name(n), country(c), height(h), weight(w), birthday(bd)
    {
    }

    std::string namae() const { return name; }
    Date tanjoubi() const { return birthday; }
    std::string kokuseki() const { return country; }
    double shinchou() const { return height; }
    double taijuu() const { return weight; }

    double bmi() const {              // 肥満指数BMI
        return weight / height / height * 10000;
    }
    double standard_w() const {       // 標準体重(kg)
        return height * height * 22 / 10000;
    }
};

#endif

// HumanTest.cpp
#include <iomanip>
#include <iostream>
#include <string>
#include "Human.h"
using namespace std;

int main() {
    Human saitou("斉藤とまと", "日本", 168.5, 55.0, Date(2000, 1, 1));

    cout << "◆" << saitou.namae() << '\n';
    cout << "  誕生日   " << saitou.tanjoubi() << '\n';
    cout << "  国籍     " << saitou.kokuseki() << '\n';
    cout << fixed << setprecision(1);
    cout << "  身長     " << saitou.shinchou() << "cm\n";
    cout << "  体重     " << saitou.taijuu() << "kg\n";
    cout << "  BMI      " << saitou.bmi() << '\n';
    cout << "  標準体重 " << saitou.standard_w() << "kg\n";
}