First Day of a New Congress: A Guide to Proceedings on the Senate Floor [November 4, 2016] [open pdf - 570KB]
"The Constitution mandates that Congress convene at noon on January 3, unless the preceding Congress by law designated a different day. P.L. 113-201 set January 6, 2015, as the convening date of the 114th Congress. […] The majority and minority leaders usually make welcoming remarks during the day's proceedings. If an election to a Senate seat is undecided or subject to consideration by the Senate, the majority leader and other Senators might address the Senate's posture on that election. Other first-day activities may occur as a consequence of specific circumstances, such as providing for a joint session with the House to count electoral votes after a presidential election. After Senators are sworn or after organizational proceedings are completed, the Senate may turn to legislative or executive business or other activities. Following their official swearing-in on the Senate floor, newly sworn Senators gather with their families in the Old Senate Chamber for ceremonial swearing-ins with the Vice President or another official of their choosing. The ceremonial swearing-ins may be photographed and recorded. Negotiations between parties over committee sizes and ratios, committee assignments, and any party leadership changes may begin during the early organization meetings for the new Senate, which occur in November and December following a general election. The committee assignment process may continue after the beginning days of a new Congress. […] This report will be updated after the convening of the 115th Congress."
CRS Report for Congress, RS20722
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html