Article V, Section 7 of the Colorado Constitution requires the Colorado General Assembly to convene at or before 10 a.m. of the second Wednesday of January each year. Thus, customarily, the General Assembly convenes for its annual general session on either the first or second Wednesday each year.
However, every four years, the General Assembly is required by Article IV, Section 3 of the Colorado Constitution, to meet in joint session prior to the inauguration of the governor, lieutenant governor, attorney general, secretary of state, and state treasurer. That Section further requires that the inauguration of those state officers occur on the “…second Tuesday of January”.
Thus, in order for the General Assembly to meet that requirement, both chambers must convene and subsequently meet in joint session at least one day prior to the “…second Tuesday of January”.
For reference, the purpose of the joint session is for the General Assembly to receive from the Colorado Secretary of State the election results for those state officers.
States are different based on the unique constitution of each state. Here in Colorado, the people – voters specifically – have the sole authority to amend their state constitution, the legislature does not. It works that way here in Colorado because that’s how the people of Colorado wanted it to work.