请帮忙菜鸟的我... 这个程式如何篇写...

你看看有用没：
#include<iostream.h>
#include<math.h>
class Date
{
    public:
        Date()//
        {
            year=0000;
            month=00;
            day=00;
        }
        Date(int year_input,int month_input,int day_input)//
        {
            year=year_input;
            month=month_input;
            day=day_input;
        }
        void date_set(int year_input,int month_input,int day_input)//
        {
            year=year_input;
            month=month_input;
            day=day_input;
        }
        void date_output()
        {
            cout<<year<<"--"<<month<<"--"<<day<<endl;
        }
        void date_plus()
        {
            if(day+1<=get_days(month,year))
                day++;
            else
            {
                month_plus();
                day=1;
            }
        }
        void date_down()
        {
            if(day-1>=1)
                day--;
            else
            {
                month_down();
                day=get_days(month,year);
            }
        }
        void month_plus()
        {
            if(month+1<=12)
                month++;
            else
            {
                year++;
                month=1;
            }

        }
        void month_down()
        {
            if(month-1>=1)
                month--;
            else
            {
                year--;
                month=12;
            }
        }
        int days_calculate(int year_input,int month_input,int day_input)//计算两个日期间的天数
        {
            int total_days=0;
            int leapyears;
            int i;
            if(year_input==year)
            {
                for(i=1;i<month;i++)
                    total_days+=get_days(i,year);
                total_days+=day;
                for(i=1;i<month_input;i++)
                    total_days-=get_days(i,year_input);
                total_days-=day_input;
                return abs(total_days);
            }
            else if(year_input<year)
            {
                leapyears=0;
                for(i=year_input;i<year;i++)
                    if(is_leap(i))
                        leapyears++;
                total_days=(year-year_input)*365+leapyears;

                for(i=1;i<month;i++)
                    total_days+=get_days(i,year);
                total_days+=day;
                for(i=1;i<month_input;i++)
                    total_days-=get_days(i,year_input);
                total_days-=day_input;
                return abs(total_days);
            }
            else
            {
                leapyears=0;
                for(i=year;i<year_input;i++)
                    if(is_leap(i))
                        leapyears++;
                total_days=(year_input-year)*365+leapyears;

                for(i=1;i<month_input;i++)
                    total_days+=get_days(i,year_input);
                total_days+=day_input;
                for(i=1;i<month;i++)
                    total_days-=get_days(i,year);
                total_days-=day;
                return abs(total_days);
            }
        }
    private:
        int get_days(int month_,int year_)
        {
            switch(month_)
            {
                case 1:
                case 3:
                case 5:
                case 7:
                case 8:
                case 10:
                case 12:
                    return 31;
                    break;
                case 4:
                case 6:
                case 9:
                case 11:
                    return 30;
                    break;
                case 2:
                    if(is_leap(year_))
                        return 29;
                    else
                        return 28;
                    break;
                default:
                    return 0;
            }
        }
        bool is_leap(int year_)
        {
            if(year_%4)
                return false;
            else if(year_%100)
                return true;
            else if(year_%400)
                return false;
            return true;
        }
    private:
        int year,month,day;
};
void main()
{
    int m_year,m_month,m_Day,result;
    char m_choice;
    Date date(2008,11,26);
    cout<<"    1.日期的设置'S'；2.日期的显示'X'；3.日期加一天'A'；\n    4.日期减一天'J'；5.日期算间隔'G'；6.退出'Q'；\n\n\n"<<endl;
    while(m_choice!='Q')
    {
        cout<<"请选择："; cin>>m_choice;
        switch(m_choice)
        {
            case 'S':    cout<<"Y："; cin>>m_year;
                        cout<<"M："; cin>>m_month;
                        cout<<"D："; cin>>m_Day;
                        date.date_set(m_year,m_month,m_Day);
                        break;
            case 'X':    break;
            case 'A':    date.date_plus();                
                        break;    
            case 'J':    date.date_down();                
                        break;
            case 'G':    cout<<"    目前时间：\n\n"<<endl;                
                        date.date_output();
                        cout<<"Y："; cin>>m_year;
                        cout<<"M："; cin>>m_month;
                        cout<<"D："; cin>>m_Day;
                        result=date.days_calculate(m_year,m_month,m_Day);
                        cout<<"    间隔时间："<<result<<endl;
                        break;                        
        }
        if(m_choice!='G')  date.date_output();
    }
}