I have two teenage boys who would live on the internet 24 hours a day. I have setup different schedules for week nights and weekends. I worked around the time issue by making two separate schedules. On week nights, the schedules run from 10:00pm to 11:59pm and 12:00am to 6:30am. I have it set to block all access for these times. I have used the MAC address filter for all networked machines.
The problem is that it doesn't block the access. It doesn't shut off at 10:00 pm if they are already on. I have the time set correctly.