calculating user time and elapsed time

// Incomplete version
#include <iostream>
using namespace std;

struct Mytime
{
   int hours;
   int mins;
};

int timecmp(Mytime,Mytime);
// returns 0 if times are same
// returns >0 if first is later than second
// returns <0 if first is before second

int setTime(Mytime& t, int h, int m );
// if valid time sets hh and mm to h and m 
// and returns 0
// if invalid returns integer > 0 as error code
// error code +1 = underflow hours
// error code +2 = overflow hours
// error code +4 = underflow mins
// error code +8 = overflow mins

void display1Time(Mytime t);
// displays in form hh:mm

void elapsed(Mytime t1, Mytime t2, Mytime& duration);
// determines the time duration between t1 and t2
// t1 assumed to be earlier than t2

void main()
{
    Mytime now;
    Mytime then;
    Mytime howlong;
    
    int h,m;
    
    do // validate input
    {
        cout << "Enter start hh mm : ";
        cin >> h >> m ;
    } while (setTime(now,h,m));
    
    do
    {
        cout << "Enter finish hh mm : ";
        cin >> h >> m ;
    } while (setTime(then,h,m));
    
    elapsed(now,then,howlong);

    cout << "Time elapsed from ";
    display1Time(now);
    cout << " until ";
    display1Time(then);
    
    cout << " is ";
    display1Time(howlong);
    cout << endl;
}

int timecmp(Mytime t1,Mytime t2)
{
   if (t1.hours == t2.hours)
   {
      if (t1.mins == t2.mins)
      {
         return 0;
      }
      else // mins not same
      {
         if (t1.mins > t2.mins)
         {
            return 1; // greater than zero
         }
         else
         {
            return -1;
         }
      }
   }
   else // hours not same
   {
      if (t1.mins > t2.mins)
      {
         return 1;
      }
      else
      {
         return -1;
      }
   }
}

int setTime(Mytime& t, int h, int m )
{
    int errorCode = 0;
    if (h < 0) errorCode += 1;
    if (h > 23) errorCode += 2;
    if (m < 0) errorCode += 4;
    if (m > 59) errorCode += 8;
    if (errorCode==0){t.hours = h; t.mins = m;}
    return errorCode;
}

//////////// THE FOLLOWING FUNCTIONS ARE INCOMPLETE

void display1Time(Mytime t)
{
     cout << "00:00";
}


void elapsed(Mytime t1, Mytime t2, Mytime& duration)
{
    setTime(duration,0,0);
}

#include <iomanip>
...
...
void display1Time(Mytime t)
{
     cout << setw(2) << setfill('0') << x << ":" << setw(2) << setfill('0') << y;
}

void elapsed(Mytime t1, Mytime t2, Mytime& duration) {
   int mins1, mins2, difference;

   // Convert the times into minutes
   mins1 = t1.hours *60 + t1.mins;
   mins2 = t2.hours *60 + t2.mins;

   // Compute the difference
   difference = mins2 - mins1;

   // Convert the minutes back into hours and minutes
   duration.hours = difference / 60;
   duration.hours = difference % 60;
}

#include <unistd.h>
#include <time.h>
#include <stdio.h>
#include <string>
#include <iostream>

const int MINUTE = 60;
const int HOUR   = MINUTE * 60;
const int DAY    = HOUR * 24;

string get_elapsed(int sec)
{
    int days    =0;
    int hours   =0;
    int minutes =0;
    int seconds =0;

    char* dstr = new char;
    char* et   = new char;

    if (days    = int(sec / DAY))    sec -= DAY * days;
    if (hours   = int(sec / HOUR))   sec -= HOUR * hours;
    if (minutes = int(sec / MINUTE)) sec -= MINUTE * minutes;

    seconds = sec;
    sprintf(et, "%02d:%02d:%02d", hours, minutes, seconds);
    string res(et);

    if (days) {
        sprintf(dstr, "%s Day%s, ", days, &"s"[days == 1]);
        strncat(dstr, et, strlen(et));
        res = string(dstr);
    }

    delete dstr;
    delete et;
    return res;
}

int main(void) {

    // cache start time
    time_t start, end;
    (void)time(&start);

    // do something...
    sleep(5);

    // get end time
    (void)time(&end);

    cout << "elapsed: " << get_elapsed(end - start) << endl;
    return 0;
}