WEEK_OF_MONTH parsing in SimpleDateFormat

Question

Hello,
I am trying to use the WEEK_OF_MONTH (capital W) in SimpleDateFormat. I want to be able to do both parse() and format() of in the format "yyMMWW". I also want to use false lenient in order to have strict control.
I have seen that the first week every month (WEEK_OF_MONTH == 1) can not be parsed properly. Below is an example program demonstrating the issue.
The program tries 100 dates from Jan 1 2006 and onwards. It converts to the yyMMWW format (which always goes fine). I also try to convert back from the yyMMWW format (using parse() method) and see that it fails on some dates.
I get an parse exception like this:
060204 -> 060201 -> java.text.ParseException: Unparseable date: "060201"
060205 -> 060201 -> java.text.ParseException: Unparseable date: "060201"
060206 -> 060202 -> 060206
060207 -> 060202 -> 060206
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.GregorianCalendar;
public class SimpleDateFormatIssue {
     public static void main(String[] args) throws ParseException {
          GregorianCalendar cal = new GregorianCalendar();
          cal.setFirstDayOfWeek(Calendar.MONDAY);
          cal.setLenient(false); //Strict checkin, significant for the issue
          //System.out.println(cal.getMinimalDaysInFirstWeek()); //doesnt matter what
          SimpleDateFormat fYYMMDD = new SimpleDateFormat("yyMMdd");
          fYYMMDD.setCalendar(cal);
          SimpleDateFormat fYYMMWW = new SimpleDateFormat("yyMMWW");
          fYYMMWW.setCalendar(cal);
          Date d = fYYMMDD.parse("060101");
          for (int i = 0; i < 100; i++) {
               String outputYYMMWW = fYYMMWW.format(d);
               Date parsedYYMMWW = null;
               Exception exc = null;
               try {
                    parsedYYMMWW = fYYMMWW.parse(outputYYMMWW);
               } catch (ParseException e) {
                    exc = e;
               System.out.println(fYYMMDD.format(d) + " -> " + outputYYMMWW + " -> " + (parsedYYMMWW != null ? fYYMMDD.format(parsedYYMMWW) : exc));
               d = getDayAfter(cal,d);
     public static Date getDayAfter(Calendar cal, Date date) {
          cal.setTime(date);
          cal.add(Calendar.DAY_OF_MONTH,1);
          Date dayAfter = cal.getTime();
          return dayAfter;
So I wonder, am I doing SimpleDateFormat abuse when I want to parse a yyMMWW formated string?
Or perhaps I have a bug in my program... :)
I saw some bugs in bug parade about SimpleDateFormat and WEEK_IN_MONTH but they all appears to be fixed in Java 5 which I am using:
java -version
java version "1.5.0_06"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_06-b05)
Java HotSpot(TM) Client VM (build 1.5.0_06-b05, mixed mode, sharing)
Thank you in advance for any pointers.
/Anders

Answer 1

The ones that fail are the ones before the first Monday of the month (since you set Monday as the first day of the week). So, I guess saying you are in the first week "060201" can't be translated back to a Monday in February.
Not sure what to do about it, though. (I didn't look what, if anything, any bugs said about it.)