How do I construct an ISO 8601 datetime in C++?

Question

I\'m working with the Azure REST API and they are using this to create the request body for table storage:

DateTime.UtcNow.ToString(\"o\")

Answer 1

You can use this function which uses std::put_time with a std::ostringstream to generate the resulting std::string.

#include 
#include 
#include 
#include 
/**
 * Generate a UTC ISO8601-formatted timestamp
 * and return as std::string
 */
std::string currentISO8601TimeUTC() {
  auto now = std::chrono::system_clock::now();
  auto itt = std::chrono::system_clock::to_time_t(now);
  std::ostringstream ss;
  ss << std::put_time(gmtime(&itt), "%FT%TZ");
  return ss.str();
}
// Usage example
int main() {
    std::cout << currentISO8601TimeUTC() << std::endl;
}

Reference: https://techoverflow.net/2018/03/30/iso8601-utc-time-as-stdstring-using-c11-chrono/