Local Time Program

I am trying to create a program that will display the local time of major city throughout the world. The code that I have written so far is

Code:

//Local time - Determine the local time for the city given in user input

#include <iostream>
#include <cstdlib>
#include <string.h>
#include <cstdio>
using namespace std;

  int main(int nNumberofArgs, char* pszArgs[])
  {
      
// Header to program
      
        cout << "**************************************" << endl;
        cout << "**********Local Time Program**********" <<endl;
        cout << "**************************************" << endl << endl;

          char dateStr [9];
          char timeStr [9];
          _strdate( dateStr);

// Display the current date and time given on the computer

          printf( "The current date is %s \n", dateStr);
         _strtime( timeStr );
         printf( "The current time is %s \n", timeStr);
        cout << endl << endl;
        
// Ask user for city
        
        string city;
        cout << endl <<  "Enter the city you would like the time for: ";
        cin >> city;
      }

The problem that I am trying to solve is how to increment or decrement the time based on the time given from the computer.

Thanks in advance for the help.

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