Generate complete iso date time representation strings with fraction and timezone

I want to print an ISO 8601 conforming string of the form of the complete date time representation as in ISO

4.3.2 Complete representations

1985-04-12T10:15:30Z combined with

4.2.2.4 Representations with decimal fraction

as 23:20:50,5

combined as allowed in

4.3.3 Representations other than complete

as in the form of 19850412T101530,42+04 or 1985-04-12T10:15:30.32Z

with boost date time using the current (wall clock), but I am not even understanding how to print a simple date time string of the current time by using the boost documentation.

Solution

You say you want to print "current (wall clock)" but your example says "1985" ?...

The following will print current time in ISO format:

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

int main()
{
    auto now = boost::posix_time::microsec_clock::universal_time();

    std::cout << to_iso_extended_string(now) << std::endl;
}

Outputs:

2019-04-26T07:52:34.533296

Note: ISO time is always in UTC timezone, so you can just append the "Z" (Zulu) suffix to it.

For more details refer to the Posix_time documentation.