DST switching not considered for in BusinessCalendarImpl

BusinessCalendarImpl doesn't honor DST switching, in some special cases (less than 5 days before DST switching and 1 hour before midnight)
the following test fails:
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Test set: org.jbpm.test.timer.TimerTest
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Tests run: 17, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 1.696 sec <<< FAILURE!
testTimerELCalendarSubtract(org.jbpm.test.timer.TimerTest) Time elapsed: 0.071 sec <<< FAILURE!
junit.framework.AssertionFailedError: expected:<26> but was:<27>
at junit.framework.Assert.fail(Assert.java:47)
at junit.framework.Assert.failNotEquals(Assert.java:280)
at junit.framework.Assert.assertEquals(Assert.java:64)
at junit.framework.Assert.assertEquals(Assert.java:198)
at junit.framework.Assert.assertEquals(Assert.java:204)
at org.jbpm.test.timer.TimerTest.testTimerELCalendarSubtract(TimerTest.java:304)

to me it seems like this is cause by the BusinessCalendarImpl and the upcoming DST which leads to a wrong day of month calculation in the test and/or BusinessCalendarImpl class