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Who would have thought Margaret Thatcher's election would be the genesis of a worldwide, annual celebration of all things "Star Wars?" Yet that's exactly how May The Fourth began.

In 1979, Thatcher was congratulated on becoming the first ever female Prime Minister of Britain by the London Evening News with a half page ad that stated, "May The Fourth Be With You, Maggie. Congratulations."

"Star Wars" had been released two years earlier, and its cultural impact was enough that the pun on "May The Force Be With You," one of the movie's catchphrases, was universal enough to make sense in a British print ad.

Not the print ad, but an actual photo taken from around the same time.

The phrase continued to be in use, and picked up steam after the Internet started to let people socialize more in a short, pithy manner.

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It wasn't until 2011, though, that fans began to co-opt the day as a celebration. Toronto Underground Cinema in Canada celebrated the day with a costume contest, film festival and more. Other venues picked up on the idea, and it continued to gather momentum.

In fact, the holiday got so popular that starting in 2012, the next day was jokingly called "Revenge of the Fifth," a joke on the "Star Wars" movie title "Revenge of the Sith." It might also have something to do with that day being Cinco de Mayo, but to this day fans still like to let their "evil sides" come out the day after "Star Wars" Day.

In October of 2012, Disney purchased Lucasfilm, creators of the "Star Wars" saga. Though fans were initially afraid that "Star Wars" Day would go away, Disney instead used the opportunity to push "Star Wars" in all its stores and theme parks.

Starting on May 4, 2013, Disney Parks have had official fan celebrations — emphasis on fan, to keep with the spirit of the day — and this year Disney stores are also joining in, offering exclusive collectibles and deals on "Star Wars" merchandise.

In 2014, toy companies -- and even Lucasfilm -- got into the game, with Hasbro taking to social media with their "Black Series" of high end toys, and Lucasfilm launching the first trailer for the animated series "Star Wars Rebels."

And in 2015, the day is even more hyped up than usual, as fans prep for the impending release of "Star Wars: The Force Awakens" in December.

Whether the date will continue to be fan driven, or corporate, only time will tell. But for today at least, May The Fourth Be With You!

[NOTE: A previous version of this story was published in 2014.]