OK. So JEvents has the ability to prevent display of an event until a specified time. But there is nothing to prevent a user from creating an event 1 or 2 hours before the event occurs. i.e. I create and publish an event 1 hour from now even though my organization prohibits that.
The only manner to enforce a rule like that is to not allow users to publish events, but only create them and then an admin/approver could publish the event if it met our organization's rules for creating events for the calendar.