title: Why does unlist() kill dates in R?
body: <p>When I unlist a list of dates it turns them back into numerics. Is that normal? Any workaround other than re-applying as.Date?  </p>
  
  <pre><code>&gt; dd &lt;- as.Date(c("2013-01-01", "2013-02-01", "2013-03-01"))
  &gt; class(dd)
  [1] "Date"
  &gt; unlist(dd)
  [1] "2013-01-01" "2013-02-01" "2013-03-01"
  &gt; list(dd)
  [[1]]
  [1] "2013-01-01" "2013-02-01" "2013-03-01"
  
  &gt; unlist(list(dd))
  [1] 15706 15737 15765
  </code></pre>
  
  <p>Is this a bug?</p>