Black Friday 2010

That the day after Thanksgiving is the "official" start of the holiday shopping season may be linked together with the idea of Santa Claus parades. Parades celebrating Thanksgiving often include an appearance by Santa at the end of the parade, with the idea that 'Santa has arrived' or 'Santa is just around the corner'.
In the late 19th century and early 20th century, many Santa parades or Thanksgiving Day parades were sponsored by department stores. These include the Toronto Santa Claus Parade, in Canada, sponsored by Eaton's, and the Macy's Thanksgiving Day Parade sponsored by Macy's. Department stores would use the parades to launch a big advertising push. Eventually it just became an unwritten rule that no store would try doing Christmas advertising before the parade was over. Therefore, the day after Thanksgiving became the day when the shopping season officially started.
Later on, the fact that this marked the official start of the shopping season led to controversy. In 1939, retail shops would have liked to have a longer shopping season, but no store wanted to break with tradition and be the one to start advertising before Thanksgiving. President Franklin D. Roosevelt moved the date for Thanksgiving one week earlier, leading to much anger by the public who wound up having to change holiday plans. Some even refused the change, resulting in the U.S. citizens celebrating Thanksgiving on two separate days. Some started referring to the change as Franksgiving.