Validation of Date

#include <iostream>
#include "date.h"
 
int main() {
    std::cout << std::boolalpha << '\n';
    
    using namespace date; 
    std::cout << "Valid days" << '\n';               
    day day31(31);
    day day32 = day31 + days(1);
    std::cout << "  day31: " << day31 << "; ";
    std::cout << "day31.ok(): "  << day31.ok() << '\n';
    std::cout << "  day32: " << day32 << "; ";
    std::cout << "day32.ok(): "  << day32.ok() << '\n';
   
    std::cout << '\n';
    std::cout << "Valid months" << '\n';       
    month month1(1);
    month month0(0);
    std::cout << "  month1: " << month1 << "; ";
    std::cout << "month1.ok(): "  << month1.ok() << '\n';
    std::cout << "  month0: " << month0 << "; ";
    std::cout << "month0.ok(): "  << month0.ok() << '\n';
    std::cout << '\n';
    std::cout << "Valid years" << '\n';      
    year year2020(2020);
    year year32768(-32768);
    std::cout << "  year2020: " << year2020 << "; ";
    std::cout << "year2020.ok(): "  << year2020.ok() << '\n';
    std::cout << "  year32768: " << year32768 << "; ";
    std::cout << "year32768.ok(): "  << year32768.ok() << '\n';
    std::cout << '\n';
    std::cout << "Leap Years"  << '\n';       
    constexpr auto leapYear2016{year(2016)/2/29};
    constexpr auto leapYear2020{year(2020)/2/29};
    constexpr auto leapYear2024{year(2024)/2/29};
    std::cout << "  leapYear2016.ok(): " << leapYear2016.ok() << '\n';
    std::cout << "  leapYear2020.ok(): " << leapYear2020.ok() << '\n';
    std::cout << "  leapYear2024.ok(): " << leapYear2024.ok() << '\n';
    std::cout << '\n';
     std::cout << "No Leap Years"  << '\n';   
    constexpr auto leapYear2100{year(2100)/2/29};
    constexpr auto leapYear2200{year(2200)/2/29};
    constexpr auto leapYear2300{year(2300)/2/29};
    std::cout << "  leapYear2100.ok(): " << leapYear2100.ok() << '\n';
    std::cout << "  leapYear2200.ok(): " << leapYear2200.ok() << '\n';
    std::cout << "  leapYear2300.ok(): " << leapYear2300.ok() << '\n';
    std::cout << '\n';
    std::cout << "Leap Years"  << '\n';      
    constexpr auto leapYear2000{year(2000)/2/29};
    constexpr auto leapYear2400{year(2400)/2/29};
    constexpr auto leapYear2800{year(2800)/2/29};
    std::cout << "  leapYear2000.ok(): " << leapYear2000.ok() << '\n';
    std::cout << "  leapYear2400.ok(): " << leapYear2400.ok() << '\n';
    std::cout << "  leapYear2800.ok(): " << leapYear2800.ok() << '\n';
    std::cout << '\n';
}