Iowa Code § 541.202
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 or trust company in this state because done or performed on any legal holiday or during any time other than regular banking hours, if such payment, certification, acceptance or other transaction could have been validly done or performed on any other day; provided that nothing herein shall be construed to compel any bank or trust company in this state, which by law or custom is entitled to close for the whole or any part of any legal holiday, to keep open for the transaction of business or to perform any of the acts or transactions aforesaid on any legal holiday except at its own option.
Iowa Code § 541.202