I know that the NSDateformatter suite of functionality is a boon for mankind, but at the same time it is very confusing to me. I hope you can help me out.
Both answers from Anna Karenina and Carl doesn't work that well as they won't return month name in nominativ for some cultures. I suggest to use the proposed solution from Pascal, which solves this issue (by replacing monthSymbols with standaloneMonthSymbols)