title: accessing unspecified fields from JodaTime DateTime objects
body: <p>I have a JodaTime DateTime object parsed by <code>ISODateTimeFormat.dateTimeParser()</code> from a string that may have one or more unspecified fields, such as day in the case of "2012-05", or year in the case of "T11:55". However, it seems that these fields are always populated with default values from the Unix epoch.</p>
  
  <p>Is there any way to know which fields were actually unspecified in the input string?</p>