title: undefined reference to boost::gregorian::greg_month::as_short_string() const
body: <p>This was asked several times however I don't know what I'm doing wrong. I'm trying to get the current date subtracted by 7. Here's the Main:</p>
  
  <pre><code>#include &lt;iostream&gt;
  #include &lt;boost/date_time/gregorian/gregorian.hpp&gt;
  #include &lt;boost/date_time/date_formatting.hpp&gt;
  #include &lt;boost/date_time/gregorian/greg_month.hpp&gt;
  
  
  using namespace std;
  using namespace boost::gregorian;
  
  int main(int argc, char **argv) {
  
      time_t rawtime;
      struct tm *timeinfo;
  
      time (&amp;rawtime);
      timeinfo = localtime (&amp;rawtime);
  
      date cdate(timeinfo-&gt;tm_year+1900, timeinfo-&gt;tm_mon+1, timeinfo-&gt;tm_mday);
      cdate += date_duration(-7);
  
      string date = to_iso_string(cdate);
      cout &lt;&lt; date &lt;&lt; endl;
      return 0;
  }
  </code></pre>
  
  <p>When I try to compile it I get the following error.</p>
  
  <pre><code>E:/include/boost/date_time/date_formatting.hpp:44: undefined reference to `boost::gregorian::greg_month::as_short_string() const'
  E:/include/boost/date_time/date_formatting.hpp:49: undefined reference to `boost::gregorian::greg_month::as_long_string() const'
  </code></pre>
  
  <p>Can anyone help? I thought I included the neccessary files..</p>