title: Get current time in milliseconds using C++ and Boost
body: <p>In my thread (using boost::thread) I need to retrieve the current time in ms or less and to convert into ms:</p>
  
  <p>Actually, reading here I've found this:</p>
  
  <pre><code>tick = boost::posix_time::second_clock::local_time();
  now  = boost::posix_time::second_clock::local_time();
  </code></pre>
  
  <p>And seems to work, but after I need to have a long value of the milliseconds of the now...</p>
  
  <p>How can I do it?</p>