What is the lame duck amendment?

The 20th Amendment is referred to as the "Lame Duck Amendment" because it shortened the amount of time between election and inauguration for elected officials, and eliminated the "lame duck session" of Congress. Because of the hardship of travel when the Constitution was written, officials who were elected in November didn't take office until the following March. Thus there was a four month period where "lame ducks" sat in office: officials whose successors had already been elected. Further, Congress was required to sit every December, thus every second year there was a "lame duck session" between December and March. The 20th Amendment moved the inauguration dates from March to January. It also removed the obligation for Congress to sit every December. Instead it obligated them to sit in January, after the newly elected officials took office. Source: http://www.answers.com/topic/amendment-xx-to-the-u-s-constitution