C++ Constructor Converts from Time24 to Time12 using constructor in Time12

#include <iostream>
#include <string>
using namespace std;
class Time24/*from w  ww.j av a  2 s .co  m*/
{
   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;
   }
   int getHrs() const   { return hours; }
   int getMins() const  { return minutes; }
   int getSecs() const  { return seconds; }
};
class Time12
{
   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)
       {  }
       Time12(Time24);                //1-arg constructor
       //3-arg constructor
       Time12(bool ap, int h, int m) : pm(ap), hrs(h), mins(m)
       {  }
       void display() const
       {
          cout << hrs << ':';
          if(mins < 10)  cout << '0';  //extra zero for "01"
             cout << mins << ' ';
          string am_pm = pm ? "p.m." : "a.m.";
          cout << am_pm;
       }
};
Time12::Time12( Time24 t24 )         //1-arg constructor
{                                 //converts Time24 to Time12
    int hrs24 = t24.getHrs();         //get hours
    //find am/pm
    pm = t24.getHrs() < 12 ? false : true;
    mins = (t24.getSecs() < 30) ?     //round secs
    t24.getMins() : t24.getMins()+1;
    if(mins == 60)                    //carry mins?
    {
       mins=0;
       ++hrs24;
       if(hrs24 == 12 || hrs24 == 24)      //carry hrs?
           pm = (pm==true) ? false : true;  //toggle am/pm
    }
    hrs = (hrs24 < 13) ? hrs24 : hrs24-12; //convert hrs
    if(hrs==0)                        //00 is 12 a.m.
    { 
       hrs=12; pm=false; 
    }
}
int main()
{
      int h, m, s;
      while(true)
      {                              //get 24-hour 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);
          cout << "You entered: ";
          t24.display();
          Time12 t12 = t24;              //convert Time24 to Time12
          cout << "\n12-hour time: ";
          t12.display();
          cout << "\n\n";
      }
      return 0;
}