Today is National Biodiesel Day. Yesterday was National Corned Beef and Cabbage Day. Tomorrow is National Poultry Day, Let's Laugh Day, and Certified Nurses Day. Last Saturday, you could have celebrated Pi Day, not to be confused with Pie Day, which occurs on January 23. Next Saturday is National Fragrance Day, as well as National Single Parents Day, National French Bread Day, and National Common Courtesy Day.

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I first noticed this insane uptick in national "holidays" a couple of years ago, three max. That's when the hashtags seriously started flooding my feeds, when the PR pitches began totally overwhelming my inbox. "Not a thing!" I declared on Twitter. "Hard pass," I'd type to publicists in deleted draft after deleted draft. I was livid. These days—and all the marketing plays and SEO grabs surrounding them—made me so mad. They still make me mad.

On any given day in America, there are upwards of half a dozen fake holidays to observe, from the painfully mundane (National Tape Measure Day, July 14) to the flat-out bizarre (National Pro-Life Cupcake Day, October 9). Where the hell do these days come from? And why do so many people jump blindly on board?

In January of 2013, Marlo Anderson began compiling these days on the aptly-named (and Google-friendly) website National Day Calendar. He too had started to see an increased interest in unofficial national holidays and wanted to investigate their origins. He has since put together a list of 1,100 days; he estimates his team is still working on researching the history behind about a quarter of them.

"The first year was basically all research and development," he says. "We had a full-time employee who did nothing but surf the web. We looked for days with rich histories, and searched social media trends to see what days were popular. For some of them, it's really difficult to track down whose idea it was or how it got started, but there are also days that are pretty well-documented."

Though Congress can vote on resolutions to recognize certain days, most remain entirely unofficial.

Anderson claims his site gets "a million hits a month," and while this number (which he says references unique visitors) both can't be verified and seems wildly high, National Day Calendar does have more than 71,000 newsletter subscribers (myself included, solely for the purpose of the story of course). It also sells paper versions of its calendar (the standard size has sold out, but the large-print version is on clearance for $9.99), and is working on a daily radio spot that it plans to syndicate to stations across the country.

Though Congress can vote on resolutions to recognize certain days—like it did with Pi Day in 2009, which passed despite nay votes from Ron Paul and nine other representatives—most remain entirely unofficial. And while there is no authorized day registry, Anderson takes applications to register days on his site. Last year he received 5,000 proposals, accepting only six.

"There is nobody that makes days official, but we certainly can give people a jumpstart on their day," he explains. One of the days that made the cut was National Shower with a Friend Day, held on February 5. The inspiration was less pervy than you'd assume. Like many of these days, it was started as a marketing ploy, this time by Denver-based water filtration company New Wave Enviro.

As the National Day Calendar reads, "Winter is the coldest and loneliest season of the year. With dwindling daylight and Valentine’s Day at its heart, February can often leave people feeling dejected and somber. National Shower with a Friend Day injects a bit of humor into the season while also serving to educate people on the benefits of showering in fresh, filtered water (and the effects of chlorine)."

Yes, fake national holidays are peak #brand. When Michael Kleinman created National Underwear Day in 2003, it was to differentiate his company, Freshpair, from the competition. Kleinman, who left Freshpair in 2011 and is now the CEO of Underwear Expert, decided the day needed to center around an actual event involving models in nothing but, well, underwear.

"We paraded 20 models in underwear around New York in Times Square and Union Square, and gave them clipboards with questionnaires," he says. "At the time, the company was really, really young, so we screenprinted the name of the company on the back of the underwear and had temporary tattoos. We interacted with the public, and it was so exciting."

Kleinman says he did a couple dozen radio interviews on the first National Underwear Day because "people kept calling." The next year, CNN covered the made-up holiday. In 2005, Fresh Pair held an underwear runway show right in the middle of Times Square; in 2008, the event moved indoors and attracted guests like Tyson Beckford, Lydia Hearst, Russell Simmons, and some Real Housewives.

Then the recession came, and the holiday went online-only. In 2013, Freshpair attempted one last IRL viral stunt—trying to break the world record for largest gathering of people in their underwear—in Times Square. "A, they failed at it," says Kleinman, who exited the company two years prior, "and B, it was an embarrassment. I never would’ve done anything like that. The event was embarrassing."

It's clear Kleinman feels intense ownership over the fake day he did indeed found: "National Underwear Day is Freshpair’s event. There were many underwear brands involved"—2013's event was sponsored by Wacoal, Tommy Hilfiger, Under Armour, and a slew of other companies—"but it’s Freshpair’s National Underwear Day. Other people have tried to copy it, unsuccessfully. It's one thing if it's an underwear manufacturer celebrating National Underwear Day, it's something else if a retailer is copying your marketing idea."

A National Pie Day ad for Labor Day, a movie that was released on neither day. Photo: APC

While many of these holidays were born out of marketing schemes (see: IHOP's National Pancake Day), even more have been hijacked by brands; this is true of food holidays in particular. Take National Pie Day, for example. In 1975, a school teacher in Colorado named Charlie Papazian declared his birthday National Pie Day. In 1986, the American Pie Council co-opted it to celebrate the 75th anniversary of Crisco. (Don't get me started on the arbitrariness of 75th anniversaries.)

And, fun fact, the APC struck up a partnership with Paramount Pictures and its film Labor Day to promote National Pie Day because the movie has a pie-making scene in it and was released near Pie Day (it came out January 31; the fake holiday in the campaign is January 23; the real holiday in the title is in September).

Marlo Anderson estimates that National Coffee Day is far and away the most popular unofficial national holiday, largely thanks to Dunkin' Donuts. While the origins of the day are unknown, Dunkin' first celebrated it in 2010. That year the brand held "The Ultimate Dunkin’ Donuts Coffee Fan Contest"; last year, customers could get a free medium cup of the brand's new roast on the day and Dunkin' extended the deal to their locations around the world. They called it the "first-ever Global Coffee Day," although September 29th (National Coffee Day in the U.S.) has been considered International Coffee Day for several years.

While Dunkin' made a whole mess of caffeinated Americans aware of National Coffee Day, Starbucks, McDonald's, Wawa, Krispy Kreme, Le Pain Quotidien, and Tim Hortons all ran promotions around the holiday in 2014. The less popular National Coffee Break Day (January 20) was started by the National Coffee Association, and is currently being ignored by thirsty, but not that thirsty, brands.

Dunkin' also observes National Donut Day. The backstory is a little more clear here, as John Costello, the president of global marketing and innovation at Dunkin' Brands, explains, "National Donut Day, held the first Friday of June each year, was originally established in 1938 by the Chicago Salvation Army to honor women who served donuts to soldiers during World War I." Dunkin' has been celebrating the holiday for the past six years by giving out free donuts to customers who buy a drink at any of the chain's locations.

Costello calls 2014 "the most successful National Donut Day in brand history," adding that, "Our loyal guests are the very essence of our brand, and these holidays are great opportunities to give back and help keep them running with our delicious coffee and donuts, on us." As Anderson explains it, "Brands are turning organic days that have some popularity into commercial opportunities."

"Brands are turning organic days that have some popularity into commercial opportunities."

Even when an official promotion isn't involved, you'll still see social media-savvy brands like Jimmy John's flirting with Wendy's on National Kiss a Ginger Day (Chester Cheetah got in on the Twitter action, too) and Sanrio shouting out National Milk Day. And then, there's the media aspect. For every publication that dismisses a pitch from David's Bridal related to National Proposal Day (this is an email several members of the Racked team received this week), there are a dozen more that hop on the SEO train, eager to grab search traffic from people wondering what exactly these days are about.

Everyone from the Wall Street Journal ("It's National Cat Day! Want a Kitten?") to MTV ("It’s National Dog Day! Here’s 11 Celeb Pooches We’re Obssessed [sic] With") to Vogue ("6 Seriously Chic Uniform-Inspired Looks in Honor of National Girl Scout Day") has tried to snag a little traffic from trending fake days.

Glamour has written listicles about Kleinman's beloved National Underwear Day, as well as National Donut Day (with the requisite Dunkin' mention) and National Orgasm Day; National Boss's Day has merited posts three years in a row.

"These are things people end up searching for—content surrounding certain holidays or days or whatever you want to call them—so we try to capitalize on that search traffic," says Lindsey Unterberger, Glamour's executive online editor. "Most of the days are celebrating fun things in life, so it's a good way to capitalize on stuff people genuinely enjoy."

It's no suprise then that when Glamour launched its beauty site Lipstick last April, the magazine wanted to mark the occasion with its own unofficial holiday. "We were like, ‘How cool would it be to have Lipstick Day?’" explains Unterberger, who also serves as Lipstick's executive editor. "Of course I was like, 'Let's just Google to see if it already exists,' and within 10 seconds I was like, 'Oh, it does!' It's July 29th, National Lipstick Day. I was like, 'That's actually really great, we will happily join the festivities in July!'"

The site ran lipstick-related content throughout the entire month, teaming up with Birchbox during the last week for a special National Lipstick Day event in the beauty startup's Soho store. "It was a natural fit for us to celebrate the day honoring our site’s name," Unterberger says. "Plus, I'm a big believer that you can change your lipstick and change your life, so it was fun to celebrate that."

Despite National Lipstick Day being covered by E!, OK!, People, InStyle, Seventeen, PopSugar, the Huffington Post, Yahoo, Vibe, The Today Show, and Women's Wear Daily last year, the origins of the fake holiday are lost on both Unterberger and me, and I'd venture to guess every single site that squeezed the SEO juice too. Plenty of these stories focus on the history of lipstick, sure, but National Lipstick Day as a thing? Nope. Nobody even questions it.