The Constitution – Article I, section 4, clauses 1-2

Elections of Congress

“The Times, Places and Manner of holding Elections for Senators and Representatives, shall be prescribed in each State by the Legislature thereof; but the Congress may at any time by Law make or alter such Regulations, except as to the Places of chusing Senators.”

Meetings of Congress Clause

Changed to noon on the third day of January by section 2 of the Twentieth Amendment, ratified January 23, 1933.

“The Congress shall assemble at least once in every Year, and such Meeting shall [be on the first Monday in December,] unless they shall by Law appoint a different Day.”