12.3派生类 时间日期

#include <iostream>

using namespace std;
class Date
{
public:
    Date(int y,int m,int d):Year(y),Month(m),Day(d) {}
    void SetDate(int y,int m,int d);
    void PrintDate();
protected:
    int Year;
    int Month;
    int Day;
};
class Time
{
public:
    Time(int h,int m,int s):Hour(h),Minute(m),Second(s) {}
    void SetTime(int h,int m,int s);
    void PrintTime();
protected:
    int Hour;
    int Minute;
    int Second;
};
class DateTime:public Date,public Time
{
public:
    DateTime(int year=0,int month=0,int day=0,int hour=0,int minute=0,int second=0):Date(year,month,day),Time(hour,minute,second) {}
    void PrintDate_Time();

};
void Date::SetDate(int y,int m,int d)
{
    Year=y;
    Month=m;
    Day=d;
}
void Date::PrintDate()
{
    cout<<"当前日期为："<<Year<<"年 "<<Month<<"月 "<<Day<<"日"<<endl;
}
void Time::SetTime(int h,int m,int s)
{
    Hour=h;
    Minute=m;
    Second=s;
}
void Time::PrintTime()
{
    cout<<"当前时间为："<<Hour<<"时 "<<Minute<<"分 "<<Second<<"秒"<<endl;
}
void DateTime::PrintDate_Time()
{
    PrintDate();
    PrintTime();
}
int main()
{
    DateTime dt_a,dt_b(2010,4,16,9,30,0);
    cout<<"dt_a: ";
    dt_a.PrintDate_Time();
    cout<<endl;
    cout<<"dt_b: ";
    dt_b.PrintDate_Time();
    dt_a.SetTime(20,00,00);
    dt_a.SetDate(2008,8,7);
    cout<<endl;
    cout<<"dt_after uptate: ";
    dt_a.PrintDate_Time();

    return 0;
}
#include <iostream>

using namespace std;
class