c++11 输出时间

std::time_t t2 = std::time(nullptr);
cout << std::put_time(std::localtime(&t), "%Y-%m-%d %H.%M.%S") << "." << msecs << endl;

auto n = chrono::system_clock::now();
auto m = n.time_since_epoch();
auto diff = duration_cast<milliseconds>(ms).count();
auto const msecs = diff % 1000;

std::time_t t = system_clock::to_time_t(n1);
cout << std::put_time(std::localtime(&t), "%Y-%m-%d %H.%M.%S") << "." << msecs << endl;

#include <string>
#include <chrono>
#include <cinttypes>
#include <ctime>
#include <sstream>
#include <iomanip>

std::string millisecond_to_str(std::int64_t milliseconds)
{
std::chrono::milliseconds ms(milliseconds);
std::chrono::time_point<std::chrono::high_resolution_clock, std::chrono::milliseconds> t1(ms);
std::time_t t = std::chrono::system_clock::to_time_t(t1);

std::stringstream ss;
auto const msecs = ms.count() % 1000;
ss << std::put_time(std::localtime(&t), "%Y-%m-%d %H.%M.%S") << "." << msecs;
return ss.str();
}