Great question! I can suggest installing our application: _Holiday Loader _that will allow you to load national, local, and religious holidays into your organizational or specific user group calendars in Clarizen as calendar exceptions.
Here is the link to the app: http://www.clarizen.com/appsmarketplace/item/holiday_loader.html.
As for the level, you can create it at the User Groups level. User Groups are a great way to sort users based on their department or location within your organization, and set the group calendar, timezone, language, etc.
See more information here: http://usermanual.clarizen.com/#19-2-managing-groups.
For further clarification, we suggest you register for one of our free daily Q&A webinars (see the link-> http://www.clarizen.com/live-demo-europe.html).These are great resources for consulting with our Customer Success Managers and visual answers to your questions. One of our experts will be able to explain it in detail in a much faster manner. You can ask for a demo during our Q&A session and we will be happy to walk you through this.
All the best,