There isn't actually a way to set up holiday hours, time offs, or availability in regards to, for example, blocking certain days.  

But what you can do is the following:

1. Create a new task called HOLIDAY - CLOSED (or name it whatever you want).

2.  Create a new customer called HOLIDAY - CLOSED and schedule them on your closed days with the hour being an all day job.  You can even make the job recurring.

Did this answer your question?