title: Daylight savings time in Python
body: <p>I am writing a program which deals a lot with timezones and crossing them. The two things I deal with most are creating a datetime object from "now" and then localizing a naive datetime object.</p>
  
  <p>To create a datetime object from now in the pacific timezone, I am currently doing this (python 2.7.2+)</p>
  
  <pre><code>from datetime import datetime
  import pytz
  la = pytz.timezone("America/Los_Angeles")
  now = datetime.now(la)
  </code></pre>
  
  <p>Is this correct with regards to DST? If not, I suppose I should be doing:</p>
  
  <pre><code>now2 = la.localize(datetime.now())
  </code></pre>
  
  <p>My question is why? Can anyone show me a case where the first is wrong and the seconds is right?</p>
  
  <p>As for my seconds question, suppose I had a naive date and time from some user input for 9/1/2012 at 8:00am in Los Angeles, CA. Is the right way to make the datetime like this:</p>
  
  <pre><code>la.localize(datetime(2012, 9, 1, 8, 0))
  </code></pre>
  
  <p>If not, how should I be building these datetimes?</p>