Mein Programm:

#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

class Clock {

public:
  // Konstruktoren
  Clock() : h(0), m(0), s(0) {}
  Clock(const Clock& c) 
    : h(c.h), m(c.m), s(c.s) {}
  Clock(int hour, int min, int sec)
    : h(hour), m(min), s(sec) {}
  // Destruktor ( nichts zu tun ... )
  ~Clock() {}

  //  Zeitvergleich
  bool operator< (const Clock& c) const;
  bool operator> (const Clock& c) const;
  bool operator== (const Clock& c) const;

  //  stelle Zeit ein
  void set(int hour, int min, int sec);
  //  gib Zeit aus
  void print() const
    { cout << h << ":" << m << ":" << s << endl; }

  friend ostream& operator<< (ostream&, const Clock&);

private:  

  int h,m,s;

};

//  Initialisierung der Uhr
void Clock::set(int hour, int min, int sec)
{
   h=hour; m=min; s=sec;    
}

//  Uhrenvergleich <
bool Clock::operator< (const Clock& c) const
{
   if (h!=c.h)
     return h<c.h;
   else if (m!=c.m)
     return m<c.m;
   else 
     return s<c.s;
}

//  Uhrenvergleich >
bool Clock::operator> (const Clock& c) const
{
   if (h!=c.h)
     return h>c.h;
   else if (m!=c.m)
     return m>c.m;
   else 
     return s>c.s;
}

//  Ausgabe
ostream& operator<< (ostream& os, const Clock& c)
{
  return os << c.h << ":" << c.m << ":" << c.s;
}

int main()
{
  //  Uhrenbeispiele
  Clock c1,c2,c3(12,36,0),c4(c3);

  c1.set(12,3,0);
  c2.set(15,32,0);

  //  Zeitausgabe
  c1.print();
  c2.print();
  c3.print();
  c4.print();

  cout << "c1 ... " << c1 << endl;
  cout << "c2 ... " << c2 << endl;
  cout << "c3 ... " << c3 << endl;
  cout << "c4 ... " << c4 << endl;

  cout << endl << "Press ENTER to continue..." << endl;   //  **
  cin.get();                                              //  **    
}

bool operator==(const Clock& Left, const Clock& Right);