title: why my 'time' class has not 'tzset' attribute
body: <p>my code:</p>
  
  <pre><code>import time
  print hasattr(time.tzset)#error
  </code></pre>
  
  <p>and why someone do this like next:</p>
  
  <pre><code>if hasattr(time, 'tzset'):
              # Move the time zone info into os.environ. See ticket #2315 for why
              # we don't do this unconditionally (breaks Windows).
              os.environ['TZ'] = self.TIME_ZONE
              time.tzset()
  </code></pre>
  
  <p>i can't understand.</p>
  
  <p>thanks</p>