Hi Dario,
Not sure about the calendar view (I guess it's possible tweaking the code a bit), but I can help you with the days off.
You should specify a contract for the year, right? After that, being an admin, you should go to the menu: HR -> List of contracts -> Click on the calendar icon
In this menu you can specify specific holidays clicking on a date and specify series of non-working days clicking on this button. In this way, you can specify the series of free days in your company.
Hope if helps!
Emilio