It seems that Apple expect me to know the difference between a standalone weekday symbol and an ordinary weekday symbol for the purposes of NSDateFormatter without any further exposition, but I'm unable to figure it out. For my locale (en_GB), the two calls return exactly the same thing. I'm not even able to find out whether the difference is a linguistic thing (maybe some languages use different words for the weekdays based on context?) or just a technical thing. Can anyone enlighten me and/or point me to the appropriate documentation?