Answer:
There aren't any federal rules requiring such a notice. If there are any requirements, you'll find them in state laws.
Editor's Note: Even if holiday closing signs are not a requirement, it is good customer service to advise them when you will close and reopen. Often posting signs at doorways one to two weeks in advance is sufficient to inform your regular customers that you will be closed. This also lets those coming to a closed branch know when you will reopen. The Banker Tools has signs available at no cost for 2008 and 2009. See the Holiday Closing Signs section here.
First published on BankersOnline.com 9/08/08