The problem happens in 3 different environments, Mac, Ubuntu and Windows Server, all with Java timezone configured as America/Sao_Paulo.
For attributes of date type, conversion errors are thrown when I try to set some specific dates, like 2015/10/18 or 2014/10/19. Those are daylight saving starting dates.
It's possible to reproduce the error using custom or OOTB content model.
More information here https://github.com/JodaOrg/joda-time/issues/146
The provided patch is not a complete fix but rather a stop gap as the assertion prevents the test from passing due to the timezone difference.