I have a question regarding business days for the purpose of the 10 days for settlement charges to be available on the GFE. I have looked up the definition of a business day which says “a day on which the offices of the business entity are open to the public for carrying on substantially all of the entity’s business functions.”

If a bank has nine branches, two of which are open on Saturday, when preparing the GFE, should Saturday be included in the 10-day count? If so, should Saturday be counted as a business day for all branches or only on the GFE from the two branches that are actually open?

YOu need to look at the entire definition, not just whether a branch is open. Can someone 'carry on substantially all of the entitiy's business functions' on a Saturday at one of the two open branches? Or is it mostly just open for deposits and check cashing?

imho, if the answer is yes then it would be a business day for your entire bank, not just those two branches. Customers are doing business with your BANK no matter what location they do it at.