Section 21. Any bank, which term for the purposes of this section shall include not only any bank as defined in section one but also, to the extent that the provisions hereof are not inconsistent with and do not infringe upon paramount federal law governing national banks, any national banking association, federal reserve bank, federal home loan bank, federal savings and loan association or federal credit union doing business in the commonwealth, may remain closed on any and all Saturdays and any and all days on which, by reason of an occasion of national mourning or rejoicing, or national emergency or local emergency affecting the community in which such bank is located, the governor shall, by proclamation, request the people of the commonwealth or of said community to close their places of business.

Wherever the commissioner determines that an emergency exists affecting banks located in the commonwealth or in any part or parts thereof, he may authorize banks located in the area or areas affected by such emergency to close any or all of their offices, and he shall make public announcement of such authorization. Further, if the commissioner determines that an emergency exists which affects a particular bank or banks or a particular office or offices thereof but not banks located in the area generally, he may authorize the particular bank or banks or office or offices so affected to close. As used in this paragraph, the word ''emergency'' shall include any condition which may interfere with the conduct of the normal operations of, or the transportation of, employees to or from, a bank or one or more offices thereof, or poses an existing or imminent threat to the safety or security of bank personnel or property, including, without limitation, conditions arising by reason of fire, flood, windstorm, snowstorm or other casualty, interruption of transportation or power facilities, war or other enemy action, and riots, civil commotion or other acts of lawlessness or violence.

Whenever the officers of a bank are of the opinion that conditions exist which pose an existing or imminent threat to the safety or security of bank personnel or property generally or at any one or more offices thereof, they may close the bank or the office or offices affected by such threat, as the case may be irrespective of whether the governor has acted or the commissioner has acted under this section. As used in this section, the word ''officers'' shall mean the person or persons designated by the board of directors, board of trustees or other governing body of a bank to act for the bank in carrying out the provisions of this section or, in the absence of any such designation, the president or any other officer currently in charge of the operations of the bank or of the office or offices in question. A bank closing an office or offices pursuant to this section shall enter in the records of the next following meeting of the board of directors and board of investment the cause and time of such closing.

Any bank or office thereof which is closed by action of the commissioner under this section may remain closed until the commissioner declares that the emergency had ended; if closed by decision of the officers, the bank may remain closed until they determine that the threat has ended; and, in either event, for such further time thereafter as may reasonably be required to reopen but in any event until the normal time of opening on the next business day.

Any Saturday or proclaimed day of closing on which a bank remains closed, and any day on which a bank or anyone or more of its offices is closed during any part or all or its normal banking hours by decision of the commissioner or by decision of its officers, shall be, with respect to such bank or, if not all of its offices are closed, then with respect to those offices which are closed, a day which is neither a ''full business day'' nor a ''banking day'' as such words are used in and for purposes of chapter one hundred and six, and any act authorized, required or permitted to be performed at, or by or with respect to such bank or such office or offices, on such day, may be performed on the next succeeding business day without any liability or loss of rights resulting from such delay.

Any action taken by the commissioner in authorizing any bank to close shall be recorded in a permanent record book, of such actions, to be maintained by the commissioner.

The provisions of this section shall be construed to be in addition to and not in substitution for, or in limitation of, any other law of the commonwealth or of the United States authorizing the closing of banks or excusing delay by a bank in the performance of its duties or obligations because of emergencies or conditions beyond its control or otherwise.