Chapter 9: Task 1

#chrono.h
=======================================================================================================================================
#pragma once
#include <iostream>


namespace chrono {
    enum class Month {
        jan = 1, feb, mar, apr, may, jun, jul, aug, sep, oct, nov, dec
    };

    class Date {
    public:
        class Invalid {
            Invalid() = default;
        };
        Date(int y, Month m, int d);

        Date();

        int day() const { return d; }
        Month month() const { return m; }
        int year() const { return y; }
        void add_day(int n);
        void add_month(int n);
        void add_year(int n);

    private:
        int y;
        Month m;
        int d;

    };

    bool is_date(int y, Month m, int d);
    bool leapyear(int y);
    bool operator==(const Date& a, const Date& b);
    bool operator!=(const Date& a, const Date& b);
    std::ostream& operator<<(std::ostream& os, const Date& d);
    std::istream& operator>>(std::istream& is, Date& dd);

}
=======================================================================================================================================
#chrono.cpp
=======================================================================================================================================
#include "chrono.h"

namespace chrono {
    Date::Date(int yy, Month mm, int dd) : y(yy), m(mm), d(dd) {
        if (!is_date(yy, mm, dd)) throw Invalid{};
    }

    const Date& default_date() {
        static Date dd{ 2001, Month::jan, 1 };
        return dd;
    }

    Date::Date() : y{ default_date().year() }, m(default_date().month()), d{ default_date().day() } {

    }

    void Date::add_day(int n) {
        d+=n;
    }

    void Date::add_month(int n) {

    }

    void Date::add_year(int n) {
        if (m == Month::feb && d == 29 && !leapyear(y + n)) {
            m = Month::mar;
            d = 1;
        }
        y += n;
    }

    bool is_date(int y, Month m, int d) {
        if (d <= 0)
            return false;
        if (m < Month::jan || Month::dec < m) return false;

        int days_in_month = 31;
        switch (m) {
        case Month::feb:
            days_in_month = (leapyear(y)) ? 29 : 28;
            break;

        case Month::apr: case Month::jun: case Month::sep: case Month::nov:
            days_in_month = 30;
            break;
        }

        if (days_in_month < d) return false;
        return true;
    }

    bool leapyear(int y) {
        if((y % 4 == 0 && y % 100 != 0) || y % 400 == 0) {
            return true;
        }
        else {
            return false;
        }
    }

    bool operator==(const Date& a, const Date& b) {
        return a.year() == b.year()
            && a.month() == b.month()
            && a.day() == b.day();
    }

    bool operator!=(const Date& a, const Date& b) {
        return !(a == b);
    }

    std::ostream& operator<<(std::ostream& os, const Date& d){
        return os << '(' << d.year()
            << ", " << static_cast<int>(d.month())
            << ", " << d.day() << ')';
    }

    std::istream& operator>>(std::istream& is, Date& dd){
        int y, m, d;
        char ch1, ch2, ch3, ch4;
        is >> ch1 >> y >> ch2 >> m >> ch3 >> d >> ch4;
        if (!is) return is;
        if (ch1 != '(' || ch2 != ',' || ch3 != ',' || ch4 != ')') {
            is.clear(std::ios_base::failbit);
            return is;
        }
        dd = Date(y, Month(m), d);
        return is;
    }

    enum class Day {
        sunday, monday, tuesday, wednesday, thursday, friday, saturday
    };

    /*void day_of_week(const Date& d) {

    }

    void next_Sunday(const Date& d) {

    }

    void next_weekday(const Date& d) {

    }*/
} //chrono
=======================================================================================================================================
#main.cpp
=======================================================================================================================================
#include <iostream>
#include "chrono.h"

int main() {
    chrono::Date today{ 1963, chrono::Month::may, 32 };
    chrono::Date tomorrow = today;
    tomorrow.add_day(1);

    std::cout << today << " " << tomorrow;
}