The setting is a user based setting so each user who logs in would need to change the date format preference. I do not believe there is a way to override the setting with a global setting, but I am checking to be sure.
I have confirmed with engineering that we do not have an option to set the date format globally. Currently it is a user by user preference.
I have submitted the request for enhancement Idea to request this functionality be added to a future release. Please visit the link below to vote up the Idea and increase the chances of it being implemented.
Please let us know if you have additional questions or concerns.