problem
when running tests with mvn (surefire plugin) the locale and the timezone are not specified, thus they are taken from the system. this makes the test execution brittle. as state of now the tests only run in certain timezones, if run in CST (china standard time) for example the following test fails:

RollingCalendarTest.testVaryingNumberOfDailyPeriods:92 p=20 expected:<1224950400000> but was:<1225036800000>

solution
specify the locale and timezone in the surefire configuration of maven like this:

<argLine>-Duser.country=EN -Duser.language=en -Duser.timezone=CEST</argLine>