I have multiple displays rendered in a Calendar View (Mo/Day/Upcoming/etc.) and everything's working as it should... except I changed a setting somewhere and applied it to all pages instead of current display and now the heading for the month display uses long format of the first date in the range of context (i.e. Tuesday, October 1 2014, Thursday, November 1, 2014, etc.)
I have "fixed" the issue by hooking theme_date_nav_title() in the theme template.php and setting $params['format'] directly, but this is hacky... Where is this setting in Views?!