FULL PRODUCT VERSION :
java version "1.7.0_04"
Java(TM) SE Runtime Environment (build 1.7.0_04-b22)
Java HotSpot(TM) 64-Bit Server VM (build 23.0-b21, mixed mode)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7601]

A DESCRIPTION OF THE PROBLEM :
Calendar.clone() does not internally recalculate the calendar. Two clones in a row result in an wrong result.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
import java.text.DateFormat;
import java.util.Calendar;
import java.util.Locale;
import java.util.TimeZone;

/**
 * Calendar Clone bug. Execute with -ea!
 */
public class CalendarBug
{
    private static final DateFormat DATE_FORMAT = DateFormat.getDateInstance(DateFormat.SHORT, Locale.US);

    public static void main(String[] args)
    {
        try
        {
            assert false;
            throw new IllegalStateException("Please enabled assertions using the -ea switch");
        }
        catch (AssertionError e)
        {
            // ok, assertions are on
        }

        Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("CET"), Locale.US);

        // define some date, e.g. the 1st December (day 336 of year)
        calendar.set(2012, 11, 1, 22, 26);

        // clone the calendar
        Calendar first = (Calendar) calendar.clone();

        // set the day of the year to the day before, e.g. 30th November
        first.set(Calendar.DAY_OF_YEAR, 335);

        // if the first calendar is used, internal values are calculated
        // if you uncomment the following line, the assertions are correct
        // first.getTime();

        // clone another time
        Calendar second = (Calendar) first.clone();

        // update to the first of day
        second.set(Calendar.DAY_OF_MONTH, 1);

        assert "12/1/12".equals(DATE_FORMAT.format(calendar.getTime())) : "Expected 12/1/12 but got "
            + DATE_FORMAT.format(calendar.getTime());
        assert "11/30/12".equals(DATE_FORMAT.format(first.getTime())) : "Expected 11/30/12 but got "
            + DATE_FORMAT.format(first.getTime());
        assert "11/1/12".equals(DATE_FORMAT.format(second.getTime())) : "Expected 11/1/12 but got "
            + DATE_FORMAT.format(second.getTime());
    }
}


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The code should not throw assertions or exceptions. Calendar.clone() should internally recalculate the calendar prior of cloning.
ACTUAL -
The code throws following assertion: Exception in thread "main" java.lang.AssertionError: Expected 11/1/12 but got 12/1/12
at CalendarBug.main(CalendarBug.java:51)
Calendar.clone() does not update internal values of the calendar.

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
import java.text.DateFormat;
import java.util.Calendar;
import java.util.Locale;
import java.util.TimeZone;

/**
 * Calendar Clone bug. Execute with -ea!
 */
public class CalendarBug
{
    private static final DateFormat DATE_FORMAT = DateFormat.getDateInstance(DateFormat.SHORT, Locale.US);

    public static void main(String[] args)
    {
        try
        {
            assert false;
            throw new IllegalStateException("Please enabled assertions using the -ea switch");
        }
        catch (AssertionError e)
        {
            // ok, assertions are on
        }

        Calendar calendar = Calendar.getInstance(TimeZone.getTimeZone("CET"), Locale.US);

        // define some date, e.g. the 1st December (day 336 of year)
        calendar.set(2012, 11, 1, 22, 26);

        // clone the calendar
        Calendar first = (Calendar) calendar.clone();

        // set the day of the year to the day before, e.g. 30th November
        first.set(Calendar.DAY_OF_YEAR, 335);

        // if the first calendar is used, internal values are calculated
        // if you uncomment the following line, the assertions are correct
        // first.getTime();

        // clone another time
        Calendar second = (Calendar) first.clone();

        // update to the first of day
        second.set(Calendar.DAY_OF_MONTH, 1);

        assert "12/1/12".equals(DATE_FORMAT.format(calendar.getTime())) : "Expected 12/1/12 but got "
            + DATE_FORMAT.format(calendar.getTime());
        assert "11/30/12".equals(DATE_FORMAT.format(first.getTime())) : "Expected 11/30/12 but got "
            + DATE_FORMAT.format(first.getTime());
        assert "11/1/12".equals(DATE_FORMAT.format(second.getTime())) : "Expected 11/1/12 but got "
            + DATE_FORMAT.format(second.getTime());
    }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
Call e.g. calendar.getTime() after cloning