C++ Operator Overload Converts from Time24 to Time12 using operator in Time24

#include <iostream>
#include <string>
using namespace std;
class Time12//w  ww  .ja va  2 s  .com
{
   private:
   bool pm;                       //true = pm, false = am
   int hrs;                       //1 to 12
   int mins;                      //0 to 59
   public:                           //no-arg constructor
   Time12() : pm(true), hrs(0), mins(0)
   {  }
   //3-arg constructor
   Time12(bool ap, int h, int m) : pm(ap), hrs(h), mins(m)
   {  }
   void display() const           //format: 11:59 p.m.
   {
      cout << hrs << ':';
      if(mins < 10)
         cout << '0';             //extra zero for "01"
      cout << mins << ' ';
      string am_pm = pm ? "p.m." : "a.m.";
      cout << am_pm;
   }
};
class Time24
{
   private:
   int hours;                     //0 to 23
   int minutes;                   //0 to 59
   int seconds;                   //0 to 59
   public:                           //no-arg constructor
   Time24() : hours(0), minutes(0), seconds(0)
   {  }
   Time24(int h, int m, int s) :  //3-arg constructor
   hours(h), minutes(m), seconds(s)
   {  }
   void display() const           //format: 23:15:01
   {
      if(hours < 10)    cout << '0';
           cout << hours << ':';
      if(minutes < 10)  cout << '0';
           cout << minutes << ':';
      if(seconds < 10)  cout << '0';
           cout << seconds;
   }
   operator Time12() const;       //conversion operator
};
Time24::operator Time12() const           //conversion operator
{
   int hrs24 = hours;
   bool pm = hours < 12 ? false : true;   //find am/pm
   //round secs
   int roundMins = seconds < 30 ? minutes : minutes+1;
   if(roundMins == 60)                    //carry mins?
   {
      roundMins=0;
      ++hrs24;
      if(hrs24 == 12 || hrs24 == 24)      //carry hrs?
         pm = (pm==true) ? false : true;  //toggle am/pm
   }
   int hrs12 = (hrs24 < 13) ? hrs24 : hrs24-12;
   if(hrs12==0)                           //00 is 12 a.m.
      { hrs12=12; pm=false; }
   return Time12(pm, hrs12, roundMins);
}
int main()
{
      int h, m, s;
      while(true)
      {                              //get 24-hr time from user
          cout << "Enter 24-hour time: \n";
          cout << "   Hours (0 to 23): "; cin >> h;
          if(h > 23)                     //quit if hours > 23
             return(1);
          cout << "   Minutes: ";  cin >> m;
          cout << "   Seconds: ";  cin >> s;
          Time24 t24(h, m, s);           //make a Time24
          cout << "You entered: ";       //display the Time24
          t24.display();
          Time12 t12 = t24;              //convert Time24 to Time12
          cout << "\n12-hour time: ";    //display equivalent Time12
          t12.display();
          cout << "\n\n";
       }
       return 0;
}