TimeCount.cpp

// C++11
#include <iostream>
#include <chrono>

const auto startTime = std::chrono::system_clock::now();

// do something

const auto endTime = std::chrono::system_clock::now();
const auto elapse = endTime - startTime;
std::cout << "elapse: " << 
    std::chrono::duration_cast<std::chrono::milliseconds>(elapse).count() << "[ms]" 
    << std::endl;

TimeCountNotUseAuto.cpp

// C++11
#include <iostream>
#include <chrono>

const std::chrono::system_clock::time_point startTime = std::chrono::system_clock::now();

// do something

const std::chrono::system_clock::time_point endTime = std::chrono::system_clock::now();
std::cout << "elapse: " << 
    std::chrono::duration_cast<std::chrono::milliseconds>(endTime - startTime).count() << "[ms]" 
    << std::endl;