I have implemented a fix for the code that fails the following tests:
RollingCalendar had an issue when detecting collisions - there was a case when the first day of a year is not exactly within the first week of a year.
JoranConfigurator did not correctly resolve appender refs (eg. AsyncAppenderBase was started too early, before all appenders were attached to it) and I delayed the start of appenders after the whole configuration is built.
I have added a pull request with my fixes on GitHub.