title: How to convert between local and universal time using boost::date_time?
body: <p>How can I convert between local and UTC time (in particular, <em>from local to UTC</em>) using <code>boost::date_time</code> using a <em>current</em> system timezone? I know about <code>boost::date_time::local_adjustor</code>, but it requires a template argument which is a timezone-dependent offset.</p>
  
  <p><a href="http://www.chronos-st.org/Discovering%20the%20Local%20Time%20Zone--Why%20It&#39;s%20a%20Hard%20Problem.html" rel="noreferrer">Failing platform-independent way</a> to do that, how would I do it specifically on Linux?</p>
  
  <p>As an aside, how are non-existent time points handled during the conversion? For example if a day is one hour short due to DST, and I try to convert a time point from the missing hour, what will be the resultant universal time?</p>