title: cast string directly to IDateTime
body: <p>I am using the new version of <code>data.table</code> and especially the AWESOME <code>fread</code> function. My files contain dates that are loaded as strings (cause I don't know to do it otherwise) looking like <code>01APR2008:09:00:00</code>.</p>
  
  <p>I need to sort the data.table on those datetimes and then for the sort to be efficient to cast then in the <code>IDateTime</code> format (or anything alse I would not know yet).</p>
  
  <pre><code>&gt; strptime("01APR2008:09:00:00","%d%b%Y:%H:%M:%S")
  [1] "2008-04-01 09:00:00"
  
  &gt; IDateTime(strptime("01APR2008:09:00:00","%d%b%Y:%H:%M:%S"))
          idate    itime
  1: 2008-04-01 09:00:00
  
  &gt; IDateTime("01APR2008:09:00:00","%d%b%Y:%H:%M:%S")
  Error in charToDate(x) : 
  character string is not in a standard unambiguous format 
  </code></pre>
  
  <p>It looks like I cannot do <code>DT[ , newType := IDateTime(strptime(oldType, "%d%b%Y:%H:%M:%S"))]</code>.</p>
  
  <p>My questions are then:</p>
  
  <ol>
  <li>Is there a way to cast directly to <code>IDateTime</code> from <code>fread</code>, such that I can sort afterward efficiently?</li>
  <li>If not, what is the most efficient way to go knowing that I would like to be able to sort DT by this datetime column</li>
  </ol>