title: as.Date returning NA while converting from 'ddmmmyyyy'
body: <p>I am trying to convert the string "2013-JAN-14" into a Date as follow :</p>
  
  <pre><code>sdate1 &lt;- "2013-JAN-14"
  ddate1 &lt;- as.Date(sdate1,format="%Y-%b-%d")
  ddate1
  </code></pre>
  
  <p>but I get :</p>
  
  <pre><code>[1] NA
  </code></pre>
  
  <p>What am I doing wrong ? should I install a package for this purpose (I tried installing chron) .</p>