title: Convert milliseconds to formatted date in Rails
body: <p>I'm sure this should be simple (probably missing something obvious), but... I have a database string of milliseconds I want to convert into a US-formatted date in Rails. Figured calling <code>.to_date</code> would be my friend, but it's throwing a strange error.</p>
  
  <pre><code>article.date =&gt; "1379844601000"
  
  article.date.to_date
  NoMethodError: undefined method `div' for nil:NilClass
  </code></pre>
  
  <p>Can anyone advise the correct way to do this?</p>