I have been advising customers to create an Admin project to handle time off. In this project, I place the Time Off Request DA to allow users to request time off, have it approved and have the item place on the schedule using the Tasks application. All users are invited into this project so the task can be assigned to the requesting user. This assignment consumes their available time and slips other projects around the day. Now the user will see the task on their timesheet and can write time against the task so you will have a balance between Scheduled and Actual and can easily run reports against Admin time.
Another solution (though not as advised) has been to invite all users in as PM on the project and allow them to schedule their time from the Tasks application. They can now write actual hours against it.
I don't advise the use of Global Non-Working time as it is presented today because nothing shows up on your timesheet and the users can't write time against it. I have no accounting of Scheduled and Actual.
John F. Filicetti, PMP, MBA