title: strptime, as.POSIXct and as.Date return unexpected NA
body: <p>When I try to parse a timestamp in the following format: "Thu Nov 8 15:41:45 2012", only <code>NA</code> is returned.</p>
  
  <p>I am using Mac OS X, R 2.15.2 and Rstudio 0.97.237. The language of my OS is Dutch: I presume this has something to do with it.</p>
  
  <p>When I try <code>strptime</code>, <code>NA</code> is returned: </p>
  
  <pre><code>var &lt;- "Thu Nov 8 15:41:45 2012"
  strptime(var, "%a %b %d %H:%M:%S %Y")
  # [1] NA
  </code></pre>
  
  <p>Neither does <code>as.POSIXct</code> work:</p>
  
  <pre><code>as.POSIXct(var, "%a %b %d %H:%M:%S %Y")
  # [1] NA
  </code></pre>
  
  <p>I also tried <code>as.Date</code> on the string above but without <code>%H:%M:%S</code> components:  </p>
  
  <pre><code>as.Date("Thu Nov 8 2012", "%a %b %d %Y")
  # [1] NA
  </code></pre>
  
  <p>Any ideas what I could be doing wrong?</p>