title: pytz.astimezone not accounting for daylight savings?
body: <p>On 2013 Jun 1 I expect the "PST8PDT" timezone to behave like GMT+7, as it is daylight savings in that timezone. However, it behaves like GMT+8:</p>
  
  <pre><code>&gt;&gt;&gt; import pytz, datetime
  &gt;&gt;&gt; Pacific = pytz.timezone("PST8PDT")
  &gt;&gt;&gt; datetime.datetime(2013, 6, 1, 12, tzinfo=Pacific).astimezone(pytz.utc)
  datetime.datetime(2013, 6, 1, 20, 0, tzinfo=&lt;UTC&gt;)
  </code></pre>
  
  <p>In contrast, on 2013 Jan 1 it behaves (correctly) like GMT+8:</p>
  
  <pre><code>&gt;&gt;&gt; datetime.datetime(2013, 1, 1, 12, tzinfo=Pacific).astimezone(pytz.utc)
  datetime.datetime(2013, 1, 1, 20, 0, tzinfo=&lt;UTC&gt;)
  </code></pre>
  
  <p>What am I doing wrong? Thanks in advance!</p>