C++ multi thread

//Utility.h
#ifndef Utility_H
#define Utility_H
#include <ctime>
#include <iostream>
#include <thread>
#include <unistd.h>
#include <uuid/uuid.h>

using namespace std;

class Utility
{
public:
    static char *uuidValue;
    static char *dtValue;
    static void printTimeAndUuid3(int num);
    static void printUuidAndTime4(int num);
    static void mt5(int num);
    Utility();
    ~Utility();
    char *getTimeNow();
    char *getUuid2();

};

#endif

//Utility.cpp
#include "Model/Utility.h"

char *Utility::dtValue = (char *)malloc(20);
char *Utility::uuidValue = (char *)malloc(40);

Utility::Utility()
{  
    if (Utility::dtValue == NULL)
    {
        Utility::dtValue = (char *)malloc(20);
        cout<<"Utility::dtValue = (char *)malloc(20);"<<endl;
    }
    if (Utility::uuidValue == NULL)
    {
        Utility::uuidValue = (char *)malloc(40);
        cout<<"Utility::uuidValue = (char *)malloc(40);"<<endl;
    }
    cout << "Constructor Utility::Utility() and now is " << getTimeNow() << endl;
}

Utility::~Utility()
{    
    if (Utility::uuidValue != NULL)
    {
        free(Utility::uuidValue);
        Utility::uuidValue = NULL;
    }
    if (Utility::dtValue != NULL)
    {
        cout << "Deconstructor Utility::~Utility() and now is " << getTimeNow() << endl;
        free(Utility::dtValue);
        Utility::dtValue = NULL;
    } 
}

char *Utility::getTimeNow()
{
    time_t rawTime = time(NULL);
    struct tm tmInfo = *localtime(&rawTime);
    strftime(dtValue, 20, "%Y%m%d%H%M%S", &tmInfo);
    return dtValue;
}

char *Utility::getUuid2()
{
    uuid_t newUUID;
    uuid_generate(newUUID);
    uuid_unparse(newUUID, uuidValue);
    return uuidValue;
}

void Utility::printTimeAndUuid3(int num)
{
    Utility ul;
    for (int i = 0; i < num; i++)
    {
        cout << "T= " << ul.getTimeNow() << "," << ul.getUuid2() << endl;
        usleep(100000);
    }
}

void Utility::printUuidAndTime4(int num)
{
    Utility ul;
    for (int i = 0; i < num; i++)
    {
        cout << "U= " << ul.getUuid2() << "," << ul.getTimeNow() << endl;
        usleep(100000);
    }
}

void Utility::mt5(int num)
{
    thread t1(printTimeAndUuid3, num);
    t1.join();
    thread t2(printUuidAndTime4, num);
    t2.join();
}

#include "Model/Utility.h"

void mt64(int num);

int main(int args, char *argv[])
{
    try
    {
        mt64(atoi(argv[1]));
    }
    catch (const std::exception &e)
    {
        std::cerr << e.what() << '\n';
    } 
    return 0;
}

void mt64(int num)
{
    Utility::mt5(num);
}