Again sorry for the delay in getting to you.
I looked into this some more and the date format in the Community Calendar Settings does not change the datepicker.
We have had this asked before so I am going to post here what Barry wrote as it is a good explanation of what is going on there:
The setting you are referring to affects the dates in some places, such as the list of events (as found at example.com/community/events/list), but not others (such as the datepicker). The principle reason for this is that the component used to form the datepicker does not understand date formats expressed in the style of a PHP date() string.
However, one of our team members, Ryan, did suggest that you could add some Javascript along these lines:
https://gist.github.com/ryanurban/6073260
Some notes from Ryan:
* You may wish to override the submission form template and remove the .datepicker class, replacing it with something unique like .your-custom-class
* If you do that then please also update the code in the gist appropriately (input.datepicker might become input.your-custom-class)
So this would require some development know-how to implement but it does seem to be possible โ however to be clear this isnโt something the date format field you have referred to is intended to influence.
Does that make sense?