title: Logstash "UNIX" date format to Human Readable
body: <p>I am using logstash to parse nagios logs. Currently I have the following in my filter.</p>
  
  <pre><code>date{
          locale =&gt; en
          match =&gt;["nagios_epoch", "UNIX"]
          target =&gt; "nagios_time"
  }
  </code></pre>
  
  <p>My output is, "2015-07-21T23:16:36.000Z". How can I convert this to a human readable date/time format? Something like, Jul 21 15:05:17. I've tried using grok to separate into day, month, time, etc. but I keep running across errors. Is there an easy way to do this?</p>