Hello Graham,
Please refer to the following post where a similar issue has been discussed :
http://our.componentone.com/groups/topic/format-the-date-at-the-top-of-the-scheduler-panel/
You can set the "Date format" property from the designer but the same could not be set through code.
I have escalated this issue to the concerned team for further review.
I will get back to you as soon as I get any information from their side.
Regards,
Reema