Why such complications?
public static GregorianCalendar convertFromDMY(String dd_mm_yy) throws ParseException
{
SimpleDateFormat fmt = new SimpleDateFormat("dd-MMM-yyyy");
Date date = fmt.parse(dd_mm_yy);
GregorianCalendar cal = GregorianCalendar.getInstance();
cal.setTime(date);
return cal;
}