Working with c++ std::chrono

chrono.cpp

#include <cstdlib>
#include <iostream>
#include <chrono>

using std::chrono::steady_clock;
using std::chrono::system_clock;

constexpr inline std::chrono::seconds timeout1 =
    std::chrono::seconds(60 * 60);
constexpr inline std::chrono::minutes timeout2 =
    std::chrono::minutes(5);

std::string to_string(const std::time_t& timepoint) {
  struct tm tbuf;
  constexpr size_t bufSz = 128;
  std::string strbuf(bufSz, 0);
  std::strftime(&strbuf[0], bufSz, "%Y-%m-%d-%H:%M:%S", ::gmtime_r(&timepoint, &tbuf));
  return strbuf;
}

std::string to_string(const steady_clock::time_point& timepoint) {
  auto clock_diff = timepoint - steady_clock::now();
  time_t time_ = system_clock::to_time_t(system_clock::now() + clock_diff);
  return to_string(time_);
}

int main() {
  using clock = std::chrono::steady_clock;

  clock::duration d_timeout1 = timeout1;
  clock::duration d_timeout2 = timeout2;

  auto clock_now = clock::now();
  auto next_timepoint1 = clock::now() + d_timeout1;
  auto next_timepoint2 = clock::now() + d_timeout2;

  std::cout << to_string(clock_now) << std::endl;
  std::cout << to_string(next_timepoint1) << std::endl;
  std::cout << to_string(next_timepoint2) << std::endl;
}