Mont. Code § 32-1-483
Any bank as defined in 32-1-102 and any national bank or national banking association incorporated or organized under the laws of the United States of America and any federal reserve bank may, at its election, remain closed and refrain from the transaction of any business on Saturdays. Any Saturday on which any such bank remains closed shall be, with respect to such bank, a holiday and not a business day. Any act authorized, required, or permitted to be performed on a Saturday at or by or with respect to any bank including any national bank or national banking association and any federal reserve bank may be performed on the next succeeding business day, and no liability or loss of any rights of any kind shall result from such closing on Saturday or from the nonopening of any bank for the transaction of business on any Saturday under the authority of 32-1-483 through 32-1-485.
§ 32-1-483, MCA