title: Liberal date/time parsing in Joda-Time
body: <p>Is it possible to create a single <code>DateTimeParser</code> which would parse:</p>
  
  <ul>
  <li>dates with time given</li>
  <li>dates without time (assuming time to be start of day)</li>
  <li>times without dates (assuming date to be today)</li>
  </ul>
  
  <p>or do I need to have three separate parsers, and try parsing strings with each one?</p>
  
  <p>In other words, is it possible to define optional fields in a parser?</p>