17 CFR 201.104: Business hours.

The Headquarters office of the Commission, at 100 F Street, NE., Washington, DC 20549, is open each day, except Saturdays, Sundays, and Federal legal holidays, from 9 a.m. to 5:30 p.m., Eastern Standard Time or Eastern Daylight Saving Time, whichever is currently in effect in Washington, D.C. Federal legal holidays consist of New Year's Day; Birthday of Martin Luther King, Jr.; Presidents Day; Memorial Day; Independence Day; Labor Day; Columbus Day; Veterans Day; Thanksgiving Day; Christmas Day; and any other day appointed as a holiday in Washington, D.C. by the President or the Congress of the United States.