2 U.S.C. § 198 — Adjournment

(a) Unless Congress passes a different rule, the two Houses of Congress must follow one of two options each year: (1) End the session completely ("adjourn sine die") no later than July 31, or (2) If it's an odd-numbered year, vote — using a recorded roll-call vote in each House — no later than July 31, to instead adjourn from the Friday in August that falls at least 30 days before Labor Day, and come back on the second day after Labor Day. This must be done through a "concurrent resolution," a resolution both Houses agree to. (b) This whole section does not apply in any year where, on July 31, the United States is in a state of war that Congress has formally declared.