title: how convert unix timestamp to datetime
body: <p>I'm trying to convert this unix timestamp 
  <strong>1415115303410</strong>
  in DateTime, in this way:</p>
  
  <pre><code>private static DateTime UnixTimeStampToDateTime(long unixTimeStamp)
  {
          System.DateTime dtDateTime = new DateTime(1970, 1, 1, 0, 0, 0, 0, System.DateTimeKind.Utc);
          dtDateTime = dtDateTime.AddMilliseconds(unixTimeStamp);
          return dtDateTime;
  }
  </code></pre>
  
  <p>But I get a wrong date:
  <strong>Date: {04/11/0045 00:00:00}</strong></p>
  
  <p>NOTE: <strong>dtDateTime.AddSeconds(unixTimeStamp)</strong> throws an exception.. my number is in Milliseconds.</p>
  
  <p>with this online conversion tool <a href="http://www.epochconverter.com/" rel="noreferrer">http://www.epochconverter.com/</a> I get the right conversion: </p>
  
  <p><strong>04/11/2014 15:35:03 GMT+0:00</strong></p>
  
  <p>How I can convert this one?</p>