You can easily block off any time that you don't want to accept appointments. This is a great way to stop people booking with you during holidays, or vacation, etc.
Start by clicking on the "Create" button from the Calendar Page :
Select on "New Block":
Fill in the title of the block. (for eg. Vacation, Thanksgiving, etc):
From there, click on the date of the block from the calendar which should then allow you to click/drag on the start and end time of the block (in the day-vertical view of the calendar):
Click on "Save Block" to save any changes:
You can also create repeating blocks, by enabling the "Repeat?" option:
or example, to create a block every week for the next year, enter "Every 1 Week for 52 times".
And then hit the "Save" Button to save the block you created.