In this dojo it can bee seen that the default culture is not applied to the headers unless an override is applied. After switching cultures to GB I thought the default 'd' would show as day/month instead of month/day. However I had to override its header to apply 'd'. Is this a little bug?
Note this dojo has (what I think) useful examples of modifying the culture pattern and showing that for views you can set multiple headers:
Week - week & day headers
Month - month & week headers
Year - year & month headers
Something that wasn't clear at first.