In 1948, Harry S. Truman convened a special session of a recalled Congress. Prior to that Presidents had done so on twenty-six separate occasions. It has not been done since.
The Constitution authorizes the president to convene a session of either or both houses of Congress under "extraordinary circumstances." The looming fiscal cliff is certainly that.
On 20 December, the House of Representatives recessed for their Christmas break, with the self-created fiscal cliff looming. With the impending loss of funding for important medical benefits, unemployment payments, and defense, the Congress has no place recessing until the People's business is finished.