C++ timestamp with nanoseconds and timezone

ts.cpp

#include <chrono>
#include <iomanip>
#include <iostream>

int main() {
  auto now = std::chrono::high_resolution_clock::now();
  auto time = std::chrono::system_clock::to_time_t(now);
  auto tm = *std::gmtime(&time);
  // auto tm = *std::localtime(&time);

  auto epoch = now.time_since_epoch();
  auto us = std::chrono::duration_cast<std::chrono::microseconds>(epoch).count() % 1000000;

  std::cout << std::put_time(&tm, "%F %T.") << us << std::put_time(&tm, " %Z\n");
}

Example:

$> g++ -Wall -Wextra -pedantic -Wconversion -O3 ts.cpp && ./a.out
2016-12-29 08:06:46.407077 GMT