Date_Time(继承)

#include "iostream"

using std::cin;
using std::cout;
using std::endl;
using std::istream;
using std::ostream;


class Time
{
protected:
  int hour;
  int minute;
  int second;

public:
  Time(int h = 0, int m = 0, int s = 0)
  :hour(h), minute(m), second(s)
  {
    int s1 = second / 60;
    second = second % 60;
    minute = minute + s1;
    int m1 = minute / 60;
    minute = minute % 60;
    hour = hour + m1;
    hour = hour % 24;
  }

  Time(const Time &t)
  :hour(t.hour), minute(t.minute), second(t.second){}

  friend ostream& operator << (ostream &output,const Time &t);
  friend istream& operator >> (istream &input, Time &t);
};

class Date
{
protected:
  int year;
  int month;
  int day;

public:
  Date(int y = 0, int m = 0, int d = 0)
  :year(y), month(m), day(d)
  {}

  friend ostream& operator << (ostream &output, const Date &d);
  friend istream& operator >> (istream &input, Date &d);

};

class DateTime : public Date, public Time
{
public:
  DateTime(int y = 0, int m = 0, int d = 0, int h = 0, int mi = 0, int s = 0)
  :Date(y, m, d), Time(h, mi, s)
  {}
  friend ostream& operator << (ostream &output, const DateTime &d);
  friend istream& operator >> (istream &input, DateTime &d);
  DateTime operator + (const DateTime &d);
  DateTime operator - (const DateTime &d);
};

ostream& operator << (ostream &output,const Time &t)
{
  output << t.hour <<" h " << t.minute << " m " << t.second << " s";
  return output;
}

istream& operator >> (istream &input, Time &t)
{
  input >> t.hour >> t.minute >> t.second;
  if(t.hour < 0) t.hour = 24 - (-t.hour % 24);
  if(t.minute < 0) t.minute = 60 - (-t.minute % 60);
  if(t.second < 0) t.second = 60 - (-t.second % 60);
  int s1 = t.second / 60;
  t.second = t.second % 60;
  t.minute = t.minute + s1;
  int m1 = t.minute / 60;
  t.minute = t.minute % 60;
  t.hour = t.hour + m1;
  t.hour = t.hour % 24;
  return input;
}

ostream& operator << (ostream &output, const Date &d)
{
  output << d.year << " year " << d.month << " month " << d.day << " day";
  return output; 
}

istream& operator >> (istream &input, Date &d)
{
  cin >> d.year >> d.month >> d.day;
  return input;
}

ostream& operator << (ostream &output, const DateTime &d)
{
  output << (Date) d << " ";
  output << (Time) d;
  return output;
}

istream& operator >> (istream &input, DateTime &d)
{
  input >> d.year >> d.month >> d.day >> d.hour >> d.minute >> d.second;
  return input;
}

DateTime DateTime::operator - (const DateTime &d)
{
  return DateTime(year - d.year, month - d.month, day - d.day,hour - d.hour, minute - d.minute, second - d.second);
}

int main(int argc, char const *argv[])
{
  DateTime a(2015, 3, 2, 15, 23, 12);
  DateTime b(2015, 5, 6, 19, 27, 30);
  cout << "DateTime a = " << a << endl;
  cin >> a;
  cout << "DateTime a = " << a << endl;
  cout << "DateTime b = " << b << endl;
  cout << "b - a = " << b - a << endl;
  return 0;
}