How to US Holidays to calendar for all users?

Can anyone offer any advice as to how to add US Holidays to Calendar v7.x? I would like all users to see the holidays as calendar entries, but not be able to modify them.

Here is a link to a similar topic for Drupal 6 - How to add a distinct class for each day - for styling annual holidays

And here is a blog post by the same author as to how to go about the styling.

Any advice would be tremendously appreciated!