title: Add milliseconds to a C date
body: <p>I have parsed a date in C with strptime. </p>
  
  <p>Now I have something like this: </p>
  
  <pre><code>debugLog(DEB_INFO, "observationDateConverted: %d-%d-%d %d:%d:%d\n", 
                          result.tm_year+1900, 
                          result.tm_mon + 1, 
                          result.tm_mday, 
                          result.tm_hour, 
                          result.tm_min, 
                          result.tm_sec);
  </code></pre>
  
  <p>With the latest date received in result (struct tm)</p>
  
  <p>I have a bunch of milliseconds like this: 1396682344000 Which I want to add to that date to know the ending date.</p>
  
  <p>How should I proceed?</p>