Untitled

#include <iostream>

class Date {
    public:
        Date(int, int, int);
        void setDate(int, int, int);
        void displayDate() const;
        Date dateBefore();
        Date dateAfter();
    private:
        static bool isValid(int, int, int);
        static bool isLeapYear(int year);
        int day;
        int month;
        int year;
};

Date::Date(int d = 1, int m = 1, int y = 2000) {
    setDate(d, m, y);
}

void Date::setDate(int d, int m, int y)
{
    if(isValid(d, m, y)) {
        day = d;
        month = m;
        year = y;
    } else {
        std::cout << "Invalid date, setting date to 1/1/2000" << std::endl;
        day = 1;
        month = 1;
        year = 2000;
    }
}

void Date::displayDate() const
{
    std::cout << day / 10 << day % 10 << "/" << month / 10 << month % 10 << "/" << year / 1000 << year % 1000 / 100 << year % 100 / 10 << year % 10 << std::endl;
}

Date Date::dateBefore()
{
    Date d;
    if (day == 1) {
        switch (month)
        {
            case 1:
                d.setDate(31, 12, year - 1);
                break;
            case 2:
            case 4:
            case 6:
            case 8:
            case 9:
            case 11:
                d.setDate(30, month - 1, year);
                break;
            case 3:
                if (isLeapYear(year)) {
                    d.setDate(29, 2, year);
                } else {
                    d.setDate(28, 2, year);
                }
                break;
            default:
                d.setDate(31, month - 1, year);
                break;
        }
    } else {
        d.setDate(day - 1, month, year);
    }
    return d;
}

bool Date::isValid(int d, int m, int y)
{
    bool valid = true;
    switch (m)
    {
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:
            if (d > 31 || d < 1) {
                valid = false;
            }
            break;
        case 2:
            if (isLeapYear(y)) {
                if (d > 29 || d < 1) {
                    valid = false;
                }
            } else {
                if (d > 28 || d < 1) {
                    valid = false;
                }
            }
            break;
        default:
            if (d > 30 || d < 1) {
                valid = false;
            }
            break;
    }
    return valid;
}

bool Date::isLeapYear(int year)
{
    if (year % 4 == 0) {
        if (year % 100 == 0) {
            if (year % 400 == 0) {
                return true;
            } else {
                return false;
            }
        } else {
            return true;
        }
    } else {
        return false;
    }
}

Date Date::dateAfter()
{
    Date d;
    switch (month)
    {
    case 1:
    case 3:
    case 5:
    case 7:
    case 8:
    case 10:
        if (day == 31) {
            d.setDate(1, month + 1, year);
        } else {
            d.setDate(day + 1, month, year);
        }
        break;
    case 2:
        if (isLeapYear(year)) {
            if (day == 29) {
                d.setDate(1, month + 1, year);
            } else {
                d.setDate(day + 1, month, year);
            }
        } else {
            if (day == 28) {
                d.setDate(1, month + 1, year);
            } else {
                d.setDate(day + 1, month, year);
            }
        }
        break;
    default:
        if (day == 30) {
            d.setDate(1, month + 1, year);
        } else {
            d.setDate(day + 1, month, year);
        }
        break;
    }
    return d;
}

int main()
{
    Date d1(30, 9, 2002);
    d1.displayDate();
    d1.dateBefore().displayDate();
    d1.dateAfter().displayDate();
}