How do I set Holiday Schedules

How do I set a holiday schedule?  I did it once for an earlier Holiday and it worked ....but I forgot to schedule it ahead of time for Thanksgiving ...I  tried to schedule on the actual day and it would not work, it just kept ringing and not going to closed message.

1. Where do I find the procedure for scheduling a holiday ahead of time?

2. How do I put the phone system to after hours message earlier then the normal?

Thank you for your help.