RestKit/RestKit — pull request #1648 by yeswolf (2013-10-29 11:52:16+00:00)
Title: Separate RKISO8601DateFormatter to default value transformers. 

In other case assuming that you've added some custom DateFormatter none of it will work because every object mapping adds RKISO8601DateFormatter and it is not possible to remove it from default date formatters because no singletone instance of it exists`