(CNN) -- It used to be that an event had to be truly momentous to warrant a new holiday -- be it the birth of a prophet or a hard-won battle for statehood. But these days all that's needed to craft a commemorative day is good dose of ingenuity and a marketing plan.
Indeed, one man alone is probably responsible for most of the world's more ridiculous holidays. American Thomas Roy has invented -- and copyrighted -- over 90 holidays in the last 26 years, including No Socks Day (May 8) and Married to a Scorpio Support Day (November 18).
But when he first started brainstorming silly things to celebrate, he had no idea that some of his inventions would one day make it onto calendars and diaries. He certainly didn't imagine that anyone would observe them.
"I just started doing it on a lark," admits Roy, who used to flip through Chase's Calendar of Events -- an annual reference guide to holidays around the world -- to get ideas for the morning radio show he hosted out of Lebanon, Pennsylvania. One year, he noticed a form in the back of the book inviting readers to submit their own holidays.
"I was like, 'oh no, don't tell me this is possible,'" he recalls. For fun, he crafted Northern Hemisphere Hoodie-Hoo Day -- Roy's answer to curing cabin fever. On February 20, observers are meant to hit the streets at noon and shout, "hoodie hoo". To his surprise, the holiday was printed in the next edition. It wasn't long before various media got a hold of it and started promoting the day as a fun, off-the-wall thing to do.
Shortly afterward, the letters started coming in. Roy received invitations to Hoodie-Hoo Day celebrations. Occasionally, corporations pay him to use some of his creations. A few years ago, Entenmann's Bakery used his Eat What You Want Day in one of their ad campaigns.
"It was kind of scary," he says. "This is how politicians get into office with these nonsensical ideas, and people buy into it."
In 1985, Australian Elaine Fremont wanted an excuse to have a monthly party. She invented Bonza Bottler Day, which she celebrated on any day that matched the month (i.e, January 1, February 2 ... ). Though Fremont passed away in 1995, her sister, Gail, carried on the tradition, and the holiday has achieved a cult status in Australia.
Official holidays don't always follow logic, either. Japan has a law that states that when two holidays fall with a day between them, the middle day becomes a de facto holiday. According to Kylie Clark, a spokesperson for the Japan National Tourism Organization, it's recognized that some holidays are mainly an excuse for the populace to take time off.
"Japanese people tend to be hesitant to use their annual leave," she admits.
In recent years, bolstering awareness has been another popular reason to craft a celebration. Though special interest groups often spearhead these initiatives, sometimes a day is granted importance just because a particularly enthusiastic individual thinks it should be.
Keith Milsom could be one of the most dedicated lefties in the world. He runs an online shop -- founded as a brick-and-mortar storefront in Central London by his left-handed father in 1967 -- called Anything Left-Handed. Though hard to prove, he strongly suspects Simpsons creator Matt Groening -- himself a leftie -- used the store as his basis for Ned Flanders' shop, The Leftorium.
Several years ago, Milsom founded The Left-Handers Club, and shortly started receiving queries about starting a holiday to support left-handed people. He launched International Left-Handers' Day on August 13, 1992. The date was picked to coincide with a slow news cycle so that it would have a better shot at garnering some media attention.
"250,000 people visited our site on the day last year. Unfortunately, that doesn't always convert into orders," says Milsom. "While there's a lot of interest in left-handed products, there's also a lot of apathy."
Still, he's been contacted by dozens of people who have concocted their own Left-Handers' Day celebrations.
"It tends to be people converting their spaces in to 'lefty-only' zones. We've heard of people who own pubs and make a rule where everyone has to drink with their left hand that day. It's fairly low-key," he admits.
Ultimately, though, the true test of a holiday's validity is if it gets its own greeting card. While Hallmark denies creating holidays, the company says it employs a team of 600 to research events worth celebrating. While Hallmark isn't making Hoodie-Hoo Day cards yet, this year it started making Star Wars Day e-cards.
"We've seen the demand for that rise out of social media," says Hallmark spokesperson Kristi Ernsting, who adds that customers were creating their own "May the Fourth Be With You" e-cards through the Hallmark site. The company decided to follow suit.
"People seem to really like that phrase," she says.