You may wish to include other dates to your Overture Calendar such as public holidays. A selection of the most common feeds are provided in the Google Calendars option in the sidebar of the Settings section. Google also provides a long list of Calendars which can be found here.
It's easy to add a new feed. Just click on the button at the bottom labelled Add Field copy the feed you require in the example shown I have copied the link to the UK Public Holiday feed, and pasted it into the form input. Hit enter and your new feed will appear in the table.
To make it clear on your Calendar that these dates are part of Calendar feeds and nothing to do with your bookings and events you can select a colour to represent them. Simply click on the coloured square to see the colour picker and select a colour that is distinct making sure to choose one that has not been selected for anything else already.