要求增加成员函数实现：
⑴ 能比较两个日期的大小（重载“= =”、“>”、“<”、“>=”、“<=”、“！=”）；
⑵ 编写main( )函数测试，内容自定。
以下是我的原程序，该如何添加
#include <iostream.h>
#include <string.h>
class time
{
private:
    int hour,min,sec;
public:
    time(int h,int m,int s)
    {hour=h;min=m,sec=s;}
    void cool ()
    {cout<<hour<<":"<<min<<":"<<sec;
    if (hour>12)
        cout<<"pm"<<endl;
    else
        cout<<"am"<<endl;
    }
   
};
#include < iostream.h >
#include < string.h >
class date
{private:
int year,month,day;
public:
    date(int y,int M,int d)
    {year=y;month=M;day=d;}
    void cool ()
    {cout<<year<<"年"<<month<<"月"<<day<<"日"<<endl;
   
    if((year%4==0)&&(year%100!=0)||(year%400==0))
        cout<<"是闰年"<<endl;   
    else
        cout<<"不是闰年"<<endl;
    }
};

class datetime:public date,public time
{public:
datetime(int y,int M,int d,int h,int m,int s):date( y, M, d),time( h, m, s)
{}
void cool ()
{
    date:: cool ();
    time:: cool ();
}
};

void main()
{
   
    datetime A(1998,8,17,9,51,30);
    A.cool();
}

比较日期时间最简单的方法是将日期转化成毫秒直接进行比较。不知道你要怎么比较，如果只是简单的比较的话，感觉没有必要重载，因为日期直接转化成毫秒后就是数字之间的比较了，这样就没有必要重载。当然要是为了重载而重载的话，就直接在类定义中进行重载，具体参考C++运算符重载啊，老铁，稳住。。。。。

没学啊老铁帮忙写一段我自己模仿模仿

#include <iostream>

class datetime
{
public:
    datetime( unsigned year, unsigned month, unsigned day, unsigned hour=0, unsigned min=0, unsigned sec=0 )
        : year_(year), month_(month), day_(day), hour_(hour), min_(min), sec_(sec)
    {
    }

    bool operator< ( const datetime& dt ) const
    {
        if(year_<dt.year_) return true;
        if(year_>dt.year_) return false;

        if(month_<dt.month_) return true;
        if(month_>dt.month_) return false;

        if(day_<dt.day_) return true;
        if(day_>dt.day_) return false;

        if(hour_<dt.hour_) return true;
        if(hour_>dt.hour_) return false;

        if(min_<dt.min_) return true;
        if(min_>dt.min_) return false;

        return sec_<dt.sec_;
    }

    bool operator> ( const datetime& dt ) const
    {
        return dt<*this;
    }
    bool operator<= ( const datetime& dt ) const
    {
        return !(dt<*this);
    }
    bool operator>= ( const datetime& dt ) const
    {
        return !(*this<dt);
    }
    bool operator!= ( const datetime& dt ) const
    {
        return *this<dt || dt<*this;
    }
    bool operator== ( const datetime& dt ) const
    {
        return !(*this<dt || dt<*this);
    }

private:
    unsigned year_, month_, day_, hour_, min_, sec_;

    friend std::ostream& operator<< ( std::ostream& os, const datetime& dt );
};

std::ostream& operator<< ( std::ostream& os, const datetime& dt )
{
    return os << dt.year_ << '-' << dt.month_ << '-' << dt.day_ << ' ' << dt.hour_ << ':' << dt.min_ << ':' << dt.sec_;
}

using namespace std;

void test( const datetime& a, const datetime& b )
{
    ios_base::fmtflags flags_saved = cout.flags();
    cout.setf( ios_base::boolalpha );

    cout << a << "  < " << b << " ? " << (a <b) << '\n';
    cout << a << "  > " << b << " ? " << (a >b) << '\n';
    cout << a << " <= " << b << " ? " << (a<=b) << '\n';
    cout << a << " >= " << b << " ? " << (a>=b) << '\n';
    cout << a << " != " << b << " ? " << (a!=b) << '\n';
    cout << a << " == " << b << " ? " << (a==b) << '\n';

    cout.setf( flags_saved, ios_base::boolalpha );
}

int main( void )
{
    test( datetime(1998,8,17,9,51,30), datetime(1998,8,17,9,51,31) );
    cout << '\n';
    test( datetime(1998,8,17,9,51,30), datetime(1998,8,17,9,51,30) );
}