The U.S. Senate relies heavily on tradition and precedent, and the first day of a new Congress is no exception.
When a new Congress convenes in the beginning of January, all the legislation of the past two years has expired (with the exception of treaties), and a new legislative year has begun.
The proceedings of this first day follow a well established, but flexible routine including the swearing in of newly elected and reelected members and the election of the president pro tempore. The Senate may choose to address other administrative issues, or begin with legislative business. The Senate does not have to reorganize itself each new Congress.
Article 1, section 3 of the Constitution provides a system of staggered six-year terms for senators. At the conclusion of each two-year congress, the terms of one third of the 100 senators expire. As a consequence, the Senate is a continuing body, which allows the Senate to make any changes in its leadership, or to change committee assignments prior to opening day.
To learn more about the opening day of a new Congress, or Senate traditions, please visit the Virtual Reference Desk's Guide to Traditions.