FULL PRODUCT VERSION :
$ java -version
java version "9-ea"
Java(TM) SE Runtime Environment (build 9-ea+99-2015-12-23-184955.javare.4146.nc)
Java HotSpot(TM) 64-Bit Server VM (build 9-ea+99-2015-12-23-184955.javare.4146.nc, mixed mode)


ADDITIONAL OS VERSION INFORMATION :
Mac OS X El Capitan 10.11.2

A DESCRIPTION OF THE PROBLEM :
Building maven-changes-plugin using Java 9 ea b99 on mac, a test fails because the test believes "06 XII 2010" is a valid date for 2010-12-06 (ISO_8601).

Doing some quick research it looks like the test is valid and DateFormat is wrong. see http://www.localeplanet.com/java/cs-CZ/


REGRESSION. Last worked in version 8u60

ADDITIONAL REGRESSION INFORMATION:
Simply changing from Java 9 to Java 8 and doing 'mvn clean install' again, all tests pass.

$ java -version
java version "1.8.0_60"
Java(TM) SE Runtime Environment (build 1.8.0_60-b27)
Java HotSpot(TM) 64-Bit Server VM (build 25.60-b23, mixed mode)

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
git clone https://github.com/apache/maven-plugins ;
cd maven-plugins/maven-changes-plugin ;
JAVA_HOME=`/usr/libexec/java_home -v 1.8` ; export JAVA_HOME ;
mvn clean install ;
JAVA_HOME=`/usr/libexec/java_home -v 9` ; export JAVA_HOME ;
mvn clean install ;


EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
tests pass in Java 8
tests pass in Java 9
ACTUAL -
tests pass in Java 8
tests fail in Java 9

ERROR MESSAGES/STACK TRACES THAT OCCUR :
java.text.ParseException: Unparseable date: "06 XII 2010"
    at java.text.DateFormat.parse(DateFormat.java:366)

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
        // pattern with months as text
        String pattern = "dd MMM yyyy";

        // Czech locale
        String locale = "cs_CZ";

            Locale usedLocale = null;

                Locale[] locales = Locale.getAvailableLocales();
                for ( int i = 0; i < locales.length; i++ )
                {
                    if ( locales[i].toString().equals( locale ) )
                    {
                        usedLocale = locales[i];
                        break;
                    }
                }

            SimpleDateFormat df = new SimpleDateFormat( pattern, usedLocale );
            df.parse( string );

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

CUSTOMER SUBMITTED WORKAROUND :
I skip that test assert statement to check everything else works fine apart from this one issue.

I've never used cs_CZ locale, I'm just trying to help out testing OpenJDK.