dateStruct

#include <iostream>

struct Date
{
    enum err { OK, DAY, MONTH, YEAR};

    uint8_t day;
    uint8_t month;
    uint16_t year;

    void print();
    int make(int8_t pDay, int8_t pMonth, int16_t pYear);
    static void printError(int pErr);
    static int isLeapYear(int16_t year);
    static int daysInMonth(int8_t pMonth, int8_t pYear);
};

void Date::print()
{
    std::cout << (int)day << '.' << (int)month << '.' << year << '\n';
}

int Date::isLeapYear(int16_t pYear)
{
    return ((pYear % 4 == 0) and (pYear % 100 != 0 or pYear % 400 == 0));
}

int Date::daysInMonth(int8_t pMonth, int8_t pYear)
{
    return 30 + ((pMonth < 8 and pMonth % 2 != 0) or (pMonth >= 8 and pMonth % 2 == 0)) + (pMonth == 2)*-2 + isLeapYear(pYear);
}

int Date::make(int8_t pDay, int8_t pMonth, int16_t pYear)
{
    if (pDay < 1 or pDay > 31) { return Date::err::DAY; }
    if (pMonth < 1 or pMonth > 12 ) { return Date::err::MONTH; }
    if (pYear < 1) { return Date::err::YEAR; }
    if (pDay > daysInMonth(pMonth,pYear)) { return Date::err::DAY; }

    day = pDay;
    month = pMonth;
    year = pYear;

    return Date::err::OK;
}

void Date::printError(int pErr)
{
    if (pErr == Date::err::DAY) { std::cout << "Bad day!\n"; }
    if (pErr == Date::err::MONTH) { std::cout << "Bad month!\n"; }
    if (pErr == Date::err::YEAR) { std::cout << "Bad year!\n"; }
}

int main()
{
    std::cout << "Size of Date struct is: " << sizeof(Date) << '\n'; //No additional bytef for err enum!!! :)

    Date d1{};
    if (auto dateErr = d1.make(29, 2, 2004) > Date::err::OK)
    {
        Date::printError(dateErr);
    };
    d1.print();

    Date d2{};
    if (auto dateErr = d1.make(29, 2, 2005) > Date::err::OK)
    {
        Date::printError(dateErr);
    };
    d2.print();

    int testMonth = 2;
    int testYear = 2004;
    std::cout << "Is " << testYear << " leap year? " << Date::isLeapYear(2004) << '\n'; //Call static member function without instance
    std::cout << "How much days are in " << testMonth << " month of " << testYear << " year? " <<  Date::daysInMonth(2,2004) << '\n'; //Call static member function without instance
}