12-Hour Clock Displaying 00 hours, when incremented after 12. 24-Hour Clock ignoring increment limitation beyond 23. How can I fix this issue?

Question

#define _CRT_SECURE_NO_WARNINGS //Suppresses warnings that will block the complier.
#include <iostream>
#include <iomanip>
#include <string>
#include <Windows.h>
#include <conio.h>
using namespace std;

#pragma warning (disable : 4996) //Disables an error due to a deprecated variable localtime.
time_t t = time(NULL);
tm* timePrt = localtime(&t);

int hours = timePrt->tm_hour;
int minutes = timePrt->tm_min;
int seconds = timePrt->tm_sec;
string timestr;


int TwelveHourClock() { //Twelve hour clock function.
    int hrs = hours;
    if (hours > 12)
    {
        hrs = hours % 12;
        timestr = "PM";
    }
    else
    {
        timestr = "AM";
    }
    return hrs;
}


void TwentyFourClock() {//Twenty four clock function.
    
    if (seconds > 59) {
        seconds = 0;
        minutes += 1;
    }
    if (minutes > 59) {
        minutes = 0;
        hours += 1;
    }
    if (hours > 23) {
        hours = 0;
        minutes = 0;
        seconds = 0;
    }
}

// formats the time to transform variables on the clock into a string for display

string Formatting(int time) {
    string format = "0";
    if (time >= 0 && time <= 9) {
        format.append(to_string(time));
    }
    else {
        format = to_string(time);
    }
    return format;
}



void Display() {//For displaying the clocks.

    TwelveHourClock();

    int hour12 = TwelveHourClock();

    string Hour12;
    string Hour24;

    string min;
    string sec;

    Hour24 = Formatting(hours);
    Hour12 = Formatting(hour12);

    min = Formatting(minutes);
    sec = Formatting(seconds);


    cout << setw(60) << string(26, '*') << setw(30) << string(26, '*') << endl;
    cout << setw(60) << "*     12-Hour Clock      *" << setw(30) << "*     24-Hour Clock      *" << endl;
    cout << setw(41) << "*      " << Hour12 << ":" << min << ":" << sec << " " << "         *" << setw(13) << "*        " << Hour24 << ":" << min << ":" << sec << " " << "       *" << endl;
    cout << setw(60) << string(26, '*') << setw(30) << string(26, '*') << endl;


    cout << setw(75) << string(26, '*') << endl;
    cout << setw(75) << "*   1 - Add One Hour     *" << endl;
    cout << setw(75) << "*   2 - Add One Minute   *" << endl;
    cout << setw(75) << "*   3 - Add One Second   *" << endl;
    cout << setw(75) << "*   4 - Exit             *" << endl;
    cout << setw(75) << string(26, '*') << endl;

    cout << "Enter a menu option: ";
}
void Clear() { //Clears the screen.
    system("cls");
}

int main() {
    int userInput = 0;
    int f = 0; //Flag

    while (userInput != 4) {

        while (!kbhit() && f == 0) {

            Clear();
            Display();
            seconds++;
            Sleep(1000);
            main();

        }

        cin >> userInput;

        switch (userInput) {
        case 1:
            hours = hours + 1;
            minutes = minutes - 1;
            seconds = seconds - 1;

        case 2:
            minutes = minutes + 1;
            seconds = seconds - 1;

        case 3:
            seconds = seconds + 1;

        }

    }


    exit(0);
}

Trying to get the program to display local time on both 12-hour and 24-hour clocks and allow the user to increment the time and adjust the hours according to the appropriate clock format. Everything is running smoothly, except when the user increments the time past the 12-hour limit (for the 12-hour clock) the hours display 00 instead of 01. Also, the 24-hour clock never stops incrementing the hours, as it should display 00 hours after incremented from 23 hours, instead it continues to 24,25,26 and so on.