title: How do I convert a Unix timestamp string to time_t in C++11?
body: <h2>Short question, aka "TD;DR".</h2>
  
  <p>I have a, say, "1464478647000" string, that I guess is a UNIX timestamp. But surely it is a string containing a number that represents time, but <strong>not in a human readable format</strong>. How do I convert it to a <code>time_t</code> type so I can format it later to a formated string, like "3 minutes ago" in C++11?</p>
  
  <hr>
  
  <h2>Long question.</h2>
  
  <p>Sorry for my bad english, first of all.</p>
  
  <p>I'm totally noob at C++11, and even C++; I just learnt a little of C and that was like 10 years ago, I almost forgot how it was. On my spare time, I'm trying to do a little fork of <a href="https://github.com/JarkoreDrake/Feednix" rel="nofollow" title="Feednix">Feednix</a> (a ncurses program, written in C++11, that acts as a Feedly client for Linux console - and looks like it's dead) so it looks more like a list (kind of how <a href="http://rybczak.net/ncmpcpp/" rel="nofollow">ncmpcpp</a> or <a href="http://www.mutt.org/" rel="nofollow" title="mutt">mutt</a> look like). As the current <a href="https://github.com/JarkoreDrake/Feednix" rel="nofollow" title="Feednix">Feednix</a> implementation is not showing time of any post, I thought it would be nice to make it show the time it was published (as the web version of Feedly does, on its "Titles only" presentation).</p>
  
  <p>The thing is that following the model of what's implemented on <a href="https://github.com/JarkoreDrake/Feednix" rel="nofollow" title="Feednix">Feednix</a>, I'm pulling the 'published' data as a string object (I couldn't figure how to pull it as an integer, or directly as a <code>time_t</code> object (seems the Json library doesn't allow to do that). Said 'published' data, says Feedly API docs, is "the timestamp, in ms, when this article was published, as reported by the RSS feed (often inaccurate)." An example of that is "1452614967000".</p>
  
  <p>So how can I do to convert that string to a <code>time_t</code> object, so I can later format it to a string like "3 minutes ago" or "2 days ago"? Or is anything better I can do to get that formatted string (which is more likely)? Any help would be appreciated!</p>