I've used the approach detailed in the post below. That allows you to turn groups on and off with cron.
- In Groups create a new group called Kids
- In Adlists edit the Facebook adlist to remove it from the Default group and put it into just the Kids group
- In Clients find the kids devices in Clients and click Add, then change their group so that they are in both Default and Kids groups
You can then turn the Kids group on and off as needed using the technique below.
- All the normal devices get the usual blocking all the time from the Default group
- All the kids devices get the usual blocking plus the Facebook blocking from the Kids group, because they are in both groups
- Turning the Kids group on and off enables and disables the blocking from adlists in that group, which in this case is just that Facebook adlist
- Use cron to enable the Kids group at 7:30pm and disable the Kids group at 9pm each day
[ You may be able to turn the list off and on directly using a similar technique, but the advantage of using Groups is that you can consolidate all blocking – lists, specific domains, regexes – related to this function in one place and enable/disable in one go. ]