Final answer:
Congress can change the specific day it meets by passing a law. The original meeting date set by the Constitution was adjusted by the 20th Amendment, which now scheduling the first meeting on January 3rd each year, with provisions for change through legislation.
Step-by-step explanation:
The method by which Congress is allowed to change the specific day it meets is through the enactment of a law. According to the Constitution and various amendments, Congress has the power to determine and adjust the times it assembles. Originally, the Constitution required Congress to assemble at least once every year, with such meeting being on the first Monday in December. However, this changed with the 20th Amendment in 1933, which moved the opening day of Congress to January 3. Nevertheless, Congress retains the authority to appoint a different day by law, as stated in the Constitution's Section 4 Clause 2 and the 20th Amendment. This flexibility is essential to ensure the legislative branch can adapt its schedule to the nation's needs and unforeseen circumstances.