format any time template

format_time.cpp

inline std::string formatTime(const time_t t) {
	std::tm timeinfo = *::gmtime(&t);
	char buffer[16];
	std::strftime(buffer, sizeof(buffer), "%Y%m%d-%H%M%S", &timeinfo);
	return std::string { buffer };
}

template <typename T>
inline std::string formatTime(T&& t) {
	using clock = typename std::remove_reference<T>::type::clock;
	return formatTime(clock::to_time_t(t));
}