Why is it a thing? Black Friday explained

Mariah Carey on the radio. Red and green tinsel strewn about supermarkets. A rogue neighbor's holiday lights display. Sales.

In today's world, all these things all may come on the day after Halloween (groan). But once upon a half-century ago, Black Friday, the day after Thanksgiving, was the true gateway for all things holiday cheer and department store crowd hell.

Here's how it came to be.

First, we have to go back to the days of Franklin Delano Roosevelt. The year: 1939.

"For the first years he's president, Thanksgiving is the last Thursday of November," explains Bruce Forbes, author of America's Favorite Holidays: Candid Histories. The Friday after Thanksgiving, while not then called Black Friday, had already been designated the natural beginning for Christmas shopping.

After a few hard winters toward the end of the Great Depression, "FDR was pressured to move Thanksgiving up from the last Thursday to the next to last Thursday — for the sole economic reason of expanding the Christmas shopping season," says Forbes.

15 best deals on Black Friday 2015: NerdWallet

This caused two years of confusion because only 31 of the states followed him in changing the holiday's date, until Congress finally made the official change in 1941. (Aside 1: It's also where the term "Franksgiving" comes from. 2. According to Forbes, the classic 1941 Bing Crosby-Fred Astaire movie Holiday Inn, best known for introducing the song White Christmas, has an animation of a turkey jumping between dates on a calendar, referring to the Thanksgiving hoopla.)

Anyway, shopping on the day after Thanksgiving has always been a big deal — like a presidential proclamations and Congressional edicts kind of big deal. But where does the name come from?

While always tied to pre-Christmas excitement, the moniker "Black Friday" didn't always have a positive connotation. In the 1950s, factory managers used the term because so many workers called in sick, according to Harvard historian Nancy Koehn at Marketplace.

However, the term really caught on in the 1960s, when the Philadelphia Police Department had to deal with massive traffic jams, crowds and shoplifters during the start of the holiday shopping season.

"You think it's just about going from the red to black in retail terms, but for Philadelphia police the day was a very bad thing," says Forbes. "There was horrible crowd control, particularly because Christmas shopping mixed with the rowdy crowd from the yearly Army-Navy football game."

Perhaps Black Friday still means lines and mayhem. But it wasn't until the 1980s that store owners decided to take back the term. "Retailers realized this was a big opportunity for them financially," says Forbes. "Marketing plans were cast with this day in mind," and that's how the name was recast in a positive — or at least, commercial — light.

Now we're in a brave new world of Black Friday shopping.

With the proliferation of the Internet, Cyber Monday has become a crowd-less day of online deal-grabbing. And with more stores opening on Thanksgiving to get ahead of bargain-hungry customers, perhaps the day itself has lost some of its seasonal allure. Black Friday may no longer be the gateway to the holiday shopping season, but it continues to be the single phrase that encapsulates consumerism in America, for better or for worse.

Thanks, FDR.