title: R: How to handle times without dates?
body: <p>I have data which includes <code>Date</code> as well as <code>Time enter</code> and <code>Time exit</code>. These latter two contain data like this: <code>08:02</code>, <code>12:02</code>, <code>23:45</code> etc.</p>
  
  <p>I would like to manipulate the <code>Time eXXX</code> data - for example, substract <code>Time enter</code> from <code>Time exit</code> to work out duration, or plot the distributions of <code>Time enter</code> and <code>Time exit</code>, e.g. to see if most entries are before 10:00, or if most exits are after 17:00.</p>
  
  <p>All the packages I've looked at require a date to precede the time, e.g. <code>01/02/2012 12:33</code>.</p>
  
  <p>Is this possible, or should I simply append an identical date to every time for the sake of calculations? This seem a bit messy!</p>