I have a similiar but slightly more complex problem, and I’ve found a very simple solution!
The problem:
My incoming ISO8601 dates look like this: 2006-06-14T11:06:00+02:00
They have a timezone offset at the end.
The solution:
Use Peter Hosey’s ISO8601DateFormatter which you can download from here.
ISO8601DateFormatter *formatter = [[ISO8601DateFormatter alloc] init];
NSDate *theDate = [formatter dateFromString:dateString];
[formatter release], formatter = nil;
and
ISO8601DateFormatter *formatter = [[ISO8601DateFormatter alloc] init];
NSString *dateString = [formatter stringFromDate:[twitch dateTwitched]];
[formatter release], formatter = nil;