Holiday Hours overlapping / trigging time

@Gary388 
Good day.  I hope are well and getting ready for the holiday season.  With regards to your question, the system should prevent you from creating an overlapping holiday schedule for a site or the account.  See below for the message I received when trying to create the overlap for testing.  When the holiday hours are active, the behavior set will take precedence for the site where it is applied.

Gary,

Generally speaking, when you set the site's default business hours, it acts as a template for the user settings. As an example, if I set my HQ location default business hours for 8am - 4:30pm, all of my users are still defaulted to 24x7 availability. When I configure a specific user's business hours, the starting point is the default business hours for the site. Once I change the business hours for my user, however, it will override the default business hours setting. 

User business hour settings will take priority over the site settings.