The 112th Congress meets today

According to Section Two of the Twentieth Amendment "The Congress shall assemble at least once in every year, and such meeting shall begin at noon on the 3d day of January, unless they shall by law appoint a different day." Originally the date when a new congress began was 4th March. This was the result the Act of the Continental Congress adopted September 13, 1788, which provided ‘that the first Wednesday in March next to be the time for commencing proceedings under the Constitution.’ It happened that the first Wednesday in March 1789 was the 4th day of March. As terms of Senators and Congressmen were measured in years, noon on March 4th marked the end of one term and the start of the next.

For the first 73 Congresses, elections were held on the First Tuesday after the first Monday in November - but terms of the newly elected members did not begin until four months later. This was addressed by the 20th Amendment.

The Senate Committee on the Judiciary in its report suggested several reasons for the proposed Twentieth Amendment. It said in part:

“[W]hen our Constitution was adopted there was some reason for such a long intervention of time between the election and the actual commencement of work by the new Congress. . . . Under present conditions [of communication and transportation] the result of elections is known all over the country within a few hours after the polls close, and the Capital City is within a few days’ travel of the remotest portions of the country. . . ."

“Another effect of the amendment would be to abolish the so– called short session of Congress. . . Every other year, under our Constitution, the terms of Members of the House and one–third of the Members of the Senate expire on the 4th day of March. . . . Experience has shown that this brings about a very undesirable legislative condition. It is a physical impossibility during such a short session for Congress to give attention to much general legislation for the reason that it requires practically all of the time to dispose of the regular appropriation bills. . . . The result is a congested condition that brings about either no legislation or ill considered legislation. . . ."

Public Law 111-289 was signed by the President on 30th November, which appoints today for the convening of the first session of the One Hundred Twelfth Congress.

The last Daily Digest of the Congressional Record for the 111th Congress reads -

Senate Chamber
Program for Wednesday: Following the presentation of the certificates of election and the swearing in of elected members, there will be a required live quorum to convene the 112th Congress. All Senators are asked to report to the floor at that time. The Senate will then be in period of morning business.

appointing the day for the convening of the first session of the One Hundred Twelfth Congress

House Chamber

Program for Wednesday: Convening of the first session of the 112th Congress.

I'll be watching live - with the help of two computers - one showing the House on C-SPAN and the other showing the Senate on C-SPAN2. Events should kick off at 5pm GMT (though I've found that timing in Congress is not as precise as it is in Westminster).

CRS have produced excellent guides to the first day of a new Congress in the
House
Senate