title: How can I extract date from epoch time in BigQuery SQL
body: <ol>
  <li><p>I have date stored in <code>Epoch Time</code> and I want to extract
  <code>Date</code> from it. I tried the code below and I get <code>null</code> as output.</p>
  
  <pre><code>date_add( (timestamp( Hp.ASSIGN_TIME)), 1970-01-01,"second" ) as Extracted_date_Epoch
  </code></pre>
  
  <p>Ex time format(1424184621000000)</p></li>
  <li><p>One more question. The code below give me days correctly but not business days, it gives all days,
  is it possible to get just business days betweeen two times stored in Epoch time?</p>
  
  <pre><code>INTEGER(((Hp.ASSIGN_TIME - Hp.ARRIVAL_TIME) / 1000000) / 86400) as Days
  </code></pre></li>
  </ol>