If you are placing a hold on a deposit, you would not count Columbus day as a business day for purposes of determining availability. This is due to the definition of the term "business day" within regulation CC, and does not factor in if you are open that day or not.
From the regulation: (g) Business day means a calendar day other than a Saturday or a Sunday, January 1, the third Monday in January, the third Monday in February, the last Monday in May, July 4, the first Monday in September, the second Monday in October, November 11, the fourth Thursday in November, or December 25. If January 1, July 4, November 11, or December 25 fall on a Sunday, the next Monday is not a business day.