Jie Zhang, a professor of marketing at the University of Maryland’s Robert H. Smith School of Business, points to a 1951 mention of “Black Friday” in a New-York based trade publication — which noted that many workers simply called in sick the day after Thanksgiving in hopes of having a long holiday weekend.

Black Friday, the day after Thanksgiving, has become a quasi-holiday in the United States that’s marked by consumer discounts, shopping, and violence, and it's grown and metastasized so much that Black Friday isn't a mere day anymore: it's a week,