Calculate Time Difference....

#include<iostream.h>
#include<conio.h>
class time
{
   int hour;
   int minute;
   int second;
   public:
      time()
      {
         hour=0;
         minute=0;
         second=0;
      }
      void get_time()
      {
         cout<<"*********** START TIME/END TIME ***********"<<endl;
         cout<<"Enter Hour:";
         cin>>hour;
         cout<<"Enter Minute:";
         cin>>minute;
         cout<<"Enter Second:";
         cin>>second;
         cout<<endl;
      }
      friend void operator-(time,time);
};
void operator-(time t,time s)
{
   int a,b,c;
   a=t.hour-s.hour;
   b=t.minute-s.minute;
   c=t.second-s.second;
   cout<<"Difference Between Start Time & End Time="<<a<<"-"<<b<<"-"<<c<<endl;
}
int main()
{
   clrscr();
   time st,et;
   st.get_time();
   et.get_time();
   st-et;
   getch();
   return 0;
}