Black Friday 2010

The term's spread was gradual, however, and in 1985 the Philadelphia Inquirer reported that retailers in Cincinnati and Los Angeles were still unaware of the term.
Accounting practice
Many merchants objected to the use of a negative term to refer to one of the most important shopping days in the year. By the early 1980s, an alternative theory began to be circulated: that retailers traditionally operated at a financial loss for most of the year (January through November) and made their profit during the holiday season, beginning on the day after Thanksgiving. When this would be recorded in the financial records, once-common accounting practices would use red ink to show negative amounts and black ink to show positive amounts. Black Friday, under this theory, is the beginning of the period where retailers would no longer have losses (the red) and instead take in the year's profits (the black). The earliest known use, which like the 1966 example above was found by Bonnie Taylor-Blake of the American Dialect Society, is from 1981, again from Philadelphia, and presents the "black ink" theory as one of several competing possibilities: