title: Sorting column in R data frame by date: Fails after 1999
body: <p>The original data frame in R contains a column called <code>OrdDate</code> with values representing dates including 12/31/1999, 1/1/2007, and so on (over 230,000 of them) ranging from years 1999-2010.</p>
  
  <p>However, when I apply date ordering with R code (follows) to the data frame, the dates sort correctly for those in 1999, but do not starting with 1/1/year, displaying 1/1/2009 next, before dates like 1/1/2004 and 1/2/2000.</p>
  
  <p>Any ideas what I could do to enforce the correct date sorting on this column?</p>
  
  <p>R code: </p>
  
  <pre><code>    sorted_frame&lt;-frame1[order(as.Date(frame1$OrdDate, format="%m/%d/%y")),]
  </code></pre>