title: Convert epoch/unix to Datetime
body: <p><strong>This is question is not a duplicate, this quesitons demonstrates a problem with a method of conversion, not how to perform the conversion. Read the question in full.</strong></p>
  
  <p>I have a timestamp which I believe is a unix time stamp, when using the following converter it correctly converts the stamp</p>
  
  <p>Value:    1365151714493</p>
  
  <p><a href="http://www.epochconverter.com/" rel="noreferrer">http://www.epochconverter.com/</a></p>
  
  <p>I have looked around and found an <a href="http://www.codeproject.com/Articles/10081/UNIX-timestamp-to-System-DateTime" rel="noreferrer">example</a> on how to convert this to a datetime obect and the method seems simple, create a datetime object and set the date to the might night on 1/1/1970 and add the value as second:</p>
  
  <pre><code>public static DateTime? ConvertUnixTimeStamp(string unixTimeStamp)
  {
      return new DateTime(1970, 1, 1, 0, 0).AddSeconds(Convert.ToDouble(unixTimeStamp));
  }
  </code></pre>
  
  <p>The problem is everytime I call this mehod with the value above I get a value out of range exception.</p>
  
  <p>Do I need to do anything with the value first? the string converts to a double ok. the exception is thrown when calling the <code>AddSeconds(double)</code> methos</p>