It converts it to nearest valid date. In your case it is 2009 or 09 according to representation pattern.
I don't get you. User tries to input date of May 29, 2009, since the format is "MM/dd/yy", he suppose to input "05/29/09", but he made mistake and input as "05/29/009", the calendar accepted it as value of May 29, 9 (2000 years ago). This causes our application failed. My question is that do we need provide our own validator to prevent this, or the calendar suppose to handle this case.