You can easily create all day events in your calendar. Simply click anywhere along the "all-day" section on top of your calendar.
The event that you create will be marked as “all day” and you can select whether you want this to be a Client Appointment or Other.
If you want to block out multiple days at once, just select the date range so you can set the beginning and end date for this event. This is ideal for blocking out vacation time in your calendar.
Once you've determined the length of your event, click Done.
You will see the event name appear at the top of your calendar.