The significance of the 20th Amendment, ratified in 1933, was that it established the beginning and end dates for presidential and congressional terms, effectively changing the presidential inauguration date from March 4 to January 20. This aimed to reduce the "lame duck" period, enhancing governmental efficiency. The amendment reflected a response to the challenges faced during the transition between administrations, especially highlighted by the Great Depression. By streamlining the transition of power, the 20th Amendment has had a lasting impact on American politics and governance.