The Twentieth Amendment to the U.S Constitution created new start and end dates for the terms of office of elected federal officers including the President and members of Congress. The amendment also covers the process of succession to the office of the President and the Vice President. The primary purpose of the amendment was to reduce the time period between Election Day and the beginning of Presidential, Vice Presidential and Congressional terms. Before the Twentieth Amendment, there was a gap of four months between the holding of federal elections in November and the installation of the newly elected officials in March of the following year. As a result, Senators and Representatives, who were defeated in November could continue in office for another four months and vote on measures without concern about re-election.
Under Section 1 of the Twentieth Amendment, the presidential and vice presidential terms begin on January 20, and congressional terms begin on January 3.
Section 2 prescribes that the U.S Congress must meet at least once a year and the first meeting shall be at noon on the 3rd day of January, unless a different day is appointed by law.
Section 3 provides for the Vice President to assume office should the President elect die after getting elected but before the beginning of the term of the President. If no President is elected or chosen before the time fixed for the beginning of his term or if the elected president fails to qualify, then the elected Vice President will act as President until a President qualifies. If neither a President nor a Vice President is qualified, then Congress will declare by who shall act as President and also determine the manner in which a new President will be elected. Such appointed President will act as President until both a President and a Vice President are qualified.