View this document in context at the NYSE Regulation Rules site:
Except as may be otherwise determined by the Exchange as to particular days, the term "business day" means any day on which the Exchange is open for business: provided, however, on any business day that the banks, transfer agencies and depositories for securities in New York State are closed:
(1) Except for orders containing non-regular way settlement instructions pursuant to Rule 14, deliveries or payments ordinarily due on such a day shall be due on the following business day;
(2) such a day shall not be considered as a business day in determining the day for settlement of a contract, the day on which stock shall be quoted ex-dividend or ex-rights, or in computing interest on contracts in bonds or premiums on loans of securities; and
(3) the right to mark to the market, to make reclamation, or to close contracts under Rule 284 (other than "cash" contracts made on such a day) shall not be exercised on such a day.
For list of holidays on which the Exchange will not be open for business see Rule 51.
Amended: January 21, 1954; February 25, 2009 (NYSE-2009-17); July 1, 2009 (NYSE-2009-59).