You can find Block Dates on the Left Navigation after selecting Administration.

 You can update the Block date Calendar from first selecting a Year, Department and Group. 

After you have updated the input fields (Year, Department and Group).
You can now update the calendar in bulk or day from the month selected. 

Bulk Selection days are Monday to Friday  
You can choose multiple dates, selected dates will turn green.
Once you have finished selecting your dates click on Save.

Single days can also be selected on the Monthly View.
You can also select multiple days by clicking on the dates required and then click Save.