Wearing white in the summer makes sense. Desert dwellers have known for thousands of years that white clothing seems to keep you a little bit cooler than other colors. But wearing white only during the summer? While no one is completely sure when or why this fashion rule came into effect, the best guess is that it had something to do with snobbery in the late 1800s and early 1900s.

After the Civil War, the wives of the super-rich ruled high society with an iron fist. As more and more people became millionaires, though, it was difficult to differentiate between respectable old money families and those who only had vulgar new money. By the 1880s, to tell who was acceptable and who was not, the women who were already “in” felt it necessary to create dozens of fashion rules that everyone in the know had to follow. That way, if a woman showed up at the opera in a dress that cost more than most Americans made in a whole year, but it had the wrong sleeve length, other women would know not to give her the time of day.

Not wearing white outside the summer months was reportedly another one of these silly rules. White was for weddings and resort wear, not dinner parties in the fall. Of course, it could get extremely hot in September, and wearing white might make sense. But if you wanted to be appropriately attired you just did not do it. Labor Day became a federal holiday in 1894, and society eventually adopted it as the natural endpoint for summer fashion.

Not everyone followed this rule. Even some socialites continued to buck the trend—most famously Coco Chanel, who regularly wore white year-round. Though the rule was originally enforced by only a few hundred women, over the decades it trickled down to everyone else. By the 1950s, women’s magazines made it clear to middle class America: White clothing was dug out on Memorial Day and went back into storage after Labor Day.

These days the fashion world is much more relaxed about what colors to wear and when, but every year you will still hear people say that white after Labor Day is unacceptable, all thanks to some snobby millionaires who decided that was a fashion no-no more than 100 years ago.

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A version of this story ran in 2019; it has been updated for 2023.

This article was originally published on www.mentalfloss.com as Why Can’t You Wear White After Labor Day?.