"Создать класс Date для работы с датами в формате «год.месяц.день»

#include <iostream>
using namespace std;
 
class Date
{
    public:
        int after_a_specified_number_of_days;
        int subtraction_of_a_specified_number_of_days;
        int leap_year;
        int assignment_of_individual_parts;
        int date_comparison;
        int calculating_the_number_of_days_between_dates;
    
        
        
    private:
        int Year;
        int Year2;
        int Day;
        int Day2;
        int Day3;
        int Month;
        int Month2;
        int D;
        int D2;
            
};
 
int Date::after_a_specified_number_of_days()
{
    return(Day+Day2);
}
int Date::subtraction_of_a_specified_number_of_days()
{
    return(Day-Day3);
}
int Date::leap_year()
{
    while(Year/4=0)
    {
        cout<<"Year is a leap year";
    }
    while(Year/4!=0)
    {
        cout<<"The year is not a leap year";
    }
    
}
int Date::assignment_of_individual_parts()
{
    return(Day+Day2,Month+Month2,Year+Year2);
}
int Date::date_comparison()
{
    int D=Day;
    int D2=Day2;
    while(D < D2)
    {
       cout<<"The first date is more than the second"<<endl;    
    }
    while(D > D2)
    {
        cout<<"First date less than second"<<endl;
    }
    while(D = D2)
    {
        cout<<"The first date is equal to the second"<<endl;
    }
}
int Date::calculating_the_number_of_days_between_dates()
{
    return(Day-Day2,Month-Month2,Year-Year2);
}
void Date::set()
{
    cout<<"Enter the start date"<<endl;
    cin>>Start date;
    cout<<"Enter the number of days you want to add"<<endl;
    cin>>Day2;
    cout<<"Enter the number of days you want to subtract"<<endl;
    cin>>Day3;
    cout<<"Enter the day, month and year you want to assign"<<endl;
    cin>>Day>>Month>>Year;
    cout<<"Enter comparing dates"<<endl;
    cin>>D>>endl>>D2;
    
    
}
void Date::show()
{
    cout<<"Start date:"<<Start date<<endl;
    cout<<"Date after the specified number of days:"<<after_a_specified_number_of_days()<<endl;
    cout<<"Date after subtraction:"<<subtraction_of_a_specified_number_of_days()<<endl;
    cout<<leap_year();
    cout<<"Date after assignment:"<<assignment_of_individual_parts();
    cout<<date_comparison();
    cout<<"Days between dates:"<<calculating_the_number_of_days_between_dates();
    
}
 
 
int main()
{
    Date n1;
    n1.set();
    n1.show();
    
}

#include <iostream>
using namespace std;
 
class Date
{
public:
    int after_a_specified_number_of_days();             //Забыл все скобки и компилятор их за переменные принимает
    int subtraction_of_a_specified_number_of_days();
    int leap_year();
    int assignment_of_individual_parts();
    int date_comparison();
    int calculating_the_number_of_days_between_dates();
    void set();         //Этих двух методов вообще не было
    void show();
private:
    int Year;
    int Year2;
    int Day;
    int Day2;
    int Day3;
    int Month;
    int Month2;
    int D;
    int D2;
 
};
 
int Date::after_a_specified_number_of_days()
{
    return(Day + Day2);
}
int Date::subtraction_of_a_specified_number_of_days()
{
    return(Day - Day3);
}
int Date::leap_year()
{
    while (Year / 4 == 0)           //Второе равно забыл
    {
        cout << "Year is a leap year";
    }
    while (Year / 4 != 0)
    {
        cout << "The year is not a leap year";
    }
 
}
int Date::assignment_of_individual_parts()
{
    return(Day + Day2, Month + Month2, Year + Year2);
}
int Date::date_comparison()
{
    int D = Day;
    int D2 = Day2;
    while (D < D2)
    {
        cout << "The first date is more than the second" << endl;
    }
    while (D > D2)
    {
        cout << "First date less than second" << endl;
    }
    while (D = D2)
    {
        cout << "The first date is equal to the second" << endl;
    }
}
int Date::calculating_the_number_of_days_between_dates()
{
    return(Day - Day2, Month - Month2, Year - Year2);
}
void Date::set()
{
    cout << "Enter the start date" << endl;
    cin >> Start date;                      //Что это вообще за переменная?
    cout << "Enter the number of days you want to add" << endl;
    cin >> Day2;
    cout << "Enter the number of days you want to subtract" << endl;
    cin >> Day3;
    cout << "Enter the day, month and year you want to assign" << endl;
    cin >> Day >> Month >> Year;
    cout << "Enter comparing dates" << endl;
    cin >> D >>   D2;                       //endl??????????
 
 
}
void Date::show()
{
 
    cout << "Start date:" << Start_date << endl;        //Что это вообще за переменная?
    cout << "Date after the specified number of days:" << after_a_specified_number_of_days() << endl;
    cout << "Date after subtraction:" << subtraction_of_a_specified_number_of_days() << endl;
    cout << leap_year();
    cout << "Date after assignment:" << assignment_of_individual_parts();
    cout << date_comparison();
    cout << "Days between dates:" << calculating_the_number_of_days_between_dates();
 
}
 
 
int main()
{
    Date n1;
    n1.set();
    n1.show();
 
}

#include <iostream>
using namespace std;
 
class Date
{
public:
    Date():Year(2018),Month(1),Day(1){}
    Date(int d,int m,int y) :Year(y), Month(m), Day(d) {}
    int after_a_specified_number_of_days(int);
    int subtraction_of_a_specified_number_of_days(int);
    int leap_year();
    Date assignment_of_individual_parts(Date d2);
    void date_comparison(Date d2);
    int calculating_the_number_of_days_between_dates(Date d2);
    void set();
    void show();
 
private:
    int Year;
    int Day;
    int Month;
};
 
int Date::after_a_specified_number_of_days(int d2)
{
    return(Day + d2);
}
int Date::subtraction_of_a_specified_number_of_days(int d2)
{
    return(Day - d2);
}
int Date::leap_year()
{
    if(Year / 4 == 0)
    {
        cout << "Year is a leap year";
    }else
    {
        cout << "The year is not a leap year";
    }
 
}
Date Date::assignment_of_individual_parts(Date d2)
{
    return Date(Day + d2.Day, Month + d2.Month, Year + d2.Year);
}
void Date::date_comparison(Date d2)
{
    int D = Day;
    int D2 = d2.Day;
    if(D < D2 && Month<=d2.Month && Year<=d2.Year)
    {
        cout << "The first date is more than the second" << endl;
    }else
    if (D > D2  && Month >= d2.Month && Year >= d2.Year)
    {
        cout << "First date less than second" << endl;
    }
    else
    {
        cout << "The first date is equal to the second" << endl;
    }
}
int Date::calculating_the_number_of_days_between_dates(Date d2)
{
    return  Day - d2.Day+(Month - d2.Month*30+(Year - d2.Year)*365;
}
void Date::set()
{
    cout << "Enter the day, month and year you want to assign" << endl;
    cin >> Day >> Month >> Year;
 
 
}
void Date::show()
{
    cout << Day << '/' << Month << '/' << Year << endl;
}
 
 
int main()
{
    Date n1(2018,12,20),n2;
    n2.set();
    n1.show();
    n2.show();
 
    cout << "Date after the specified number of days:" << n1.after_a_specified_number_of_days(10) << endl;
    cout << "Date after subtraction:" << n1.subtraction_of_a_specified_number_of_days(11) << endl;
    cout << "Leap Year:" << n2.leap_year() << endl;
 
    Date n3=n1.assignment_of_individual_parts(n2);
    cout << "Date after assignment:";
    n3.show();
 
    cout << "Days between dates:" << n1.calculating_the_number_of_days_between_dates(n2);
 
    n1.date_comparison(n2);
 
}