Tomorrow marks the 79th anniversary of the first inauguration of a President on January 20. Until 1937, presidential terms began on March 4, leaving a long 4-month gap between election day and the oath of office. The need to shorten that interval was recognized by Congress during the Great Depression. Lawmakers approved the amendment on March 2, 1932 and it was ratified by enough states to take effect on January 23, 1933.
The amendment also changed the annual meeting date for Congress from the first Monday in December to January 3. That had an even greater effect on U.S. politics than the presidential date because the second session of each Congress convened after elections in which many could have been defeated and the balance of power in each house could have changed. It also meant that House members were running for reelection when they had served only half their term.
That timetable made accountability difficult and freed members from many incentives to pay attention to their voters during the second year of their term. It also freed presidents from close scrutiny until near the end of their first year in office. The 20th amendment improved both responsiveness and accountability.