title: How do you convert the following time from UTC to EST in Ruby (without Rails)?
body: <p>I am trying to covert the UTC time "2018-04-02T14:30:00Z" to EST in pure Ruby. I noticed the following discrepancy. If I parse the time in UTC using Rails and then add the EST zone_offset I get a different time than using the "in_time_zone" helper. 9:30 versus 10:30.</p>
  
  <pre><code>2.2.4 :001 &gt; t = Time.parse "2018-04-02T14:30:00Z"
   =&gt; 2018-04-02 14:30:00 UTC 
  2.2.4 :002 &gt; t + Time.zone_offset("EST")
   =&gt; 2018-04-02 09:30:00 UTC 
  2.2.4 :003 &gt; t.in_time_zone('Eastern Time (US &amp; Canada)')
   =&gt; Mon, 02 Apr 2018 10:30:00 EDT -04:00 
  </code></pre>