Nothing in any law of this state shall in any manner whatsoever affect the validity of, or render void or voidable, the payment, certification, or acceptance of a check or other negotiable instrument or any other transaction by a bank in this state because done or performed during any time other than regular banking hours or on a legal holiday, provided that nothing shall be construed herein to compel any bank in this state, which by law or custom is entitled to close at 12 noon on any Saturday or for the whole or part of any legal holiday, to keep open for transaction of business or to perform any of the acts or transactions aforesaid on any Saturday after such hour or on any legal holiday except at its option.
§ 32-1-482, MCA