title: Unix dateTime format not properly converted in swift 5
body: <p>Using alamofire İ am fetching JSON data in swift. 
  Time value is integer and have iso8601 format. When İ am converting Unix datetime which in integer format from back end gives me weird value. </p>
  
  <p><code>1570088096210</code> must have to convert to <code>GMT: Thursday, October 3, 2019 7:34:56.210 AM</code> but giving me <code>51724-02-10T10:16:00+00:00</code></p>
  
  <blockquote>
    <p>Code:</p>
  </blockquote>
  
  <pre><code> let dateValue = Double(AppData.time ?? 0)
   let dateFinal = Date(timeIntervalSince1970: dateValue).formattedISO8601
  </code></pre>