Final answer:
Congress has met for two-year terms starting in 1789, convening at least once per year with the current rule specifying January 3 at noon as the beginning unless changed by law.
Step-by-step explanation:
Congress has met for two-year terms, known as a 'session of Congress,' beginning with the first such meeting in 1789. Initially, under the Articles of Confederation, the nation's legislative body was termed the Congress of the Confederation, which met from 1781 until 1789. After the ratification of the Constitution, the structure and operations of Congress evolved, eventually leading to the establishment of the rules currently in place today.
According to Section 4 Clause 2, Congress is mandated to hold at least one session per year. This was revised by the 20th Amendment in 1933 which set the start date for Congress to convene as January 3 at noon, unless a different day is appointed by law. This sequence of regular meetings has been key in maintaining the legislative rhythm of the U.S. government since the beginning.