qt - 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")

Which produces:

2012-03-02T04:07:34.0218628Z

It is called "round-trip" and apparently it's an ISO standard (see http://en.wikipedia.org/wiki/ISO_8601) but I have no idea how to replicate it after reading the wiki article.

Does anyone know if Boost has support for this, or possibly Qt?

Answer 1

If the time to the nearest second is precise enough, you can use strftime:

#include <ctime>
#include <iostream>

int main() {
    time_t now;
    time(&now);
    char buf[sizeof "2011-10-08T07:07:09Z"];
    strftime(buf, sizeof buf, "%FT%TZ", gmtime(&now));
    // this will work too, if your compiler doesn't support %F or %T:
    //strftime(buf, sizeof buf, "%Y-%m-%dT%H:%M:%SZ", gmtime(&now));
    std::cout << buf << "
";
}

If you need more precision, you can use Boost:

#include <iostream>
#include <boost/date_time/posix_time/posix_time.hpp>

int main() {
    using namespace boost::posix_time;
    ptime t = microsec_clock::universal_time();
    std::cout << to_iso_extended_string(t) << "Z
";
}