Don't worry, this isn't another one of those Earth holidays you're not sure how to observe. It's a Star Trek thing. First introduced in episode one of season two (Amok Time): Pon Farr is part of the male Vulcan life cycle. It happens every seven years.
At least, it's freaky to us.
"It is a thing no out-worlder may know except those very few who have been involved. A Vulcan understands, but even we do not speak of it among ourselves. It is a deeply personal thing. Can you see that, Captain, and understand?"
For Vulcans it's a normal, if somewhat uncomfortable part of life. Vulcan males begin to run a fever, they become volatile and unpredictable, and they will ultimately die unless they mate (or engage in a ritual battle called kal-if-fee).
"It strips our minds from us. It brings a madness which rips away our veneer of civilisation. It is the pon farr. The time of mating. There are precedents in nature, Captain. The giant eelbirds of Regulus Five, once each eleven years they must return to the caverns where they hatched. On your Earth, the salmon. They must return to that one stream where they were born, to spawn or die in trying."
Seems simple, right?
Okay, no. It really doesn't. But bear with me. Because this episode inspired thousands fanworks that would shape the way fans engage with media today.
The Ring of Soshern
Though the story is dated as being written in 1975, it's possible that author Jennifer Guttridge wrote and circulated this story much earlier. While there were a few Spock & Kirk themed fanzines circulating as early as 1967, this story may have been on of the first slash fics ever written. While it may seem a bit cliche to readers today, at the time it set the tone for slash fic and in fact invented those cliches. And it's all about pon farr.
"One of the earliest K/S stories. Photocopies of the manuscript circulated very privately, before it was finally published in 1987 in Alien Brothers. In the story Kirk and Spock beam down to a previously unexplored planet to investigate some mysterious sensor readings. Through a miscalculation the Enterprise gets caught in an ion storm and must leave them behind. Kirk and Spock are left deserted on the planet, not knowing when the ship will be able to return for them, for there will be much damage from the ion storm that Scotty will have to fix first. Over the next days Kirk and Spock have to deal with dangerous plants, dinosaur-like creatures, and even some shaggy humanoids. They each in turn get wounded and must be tenderly ministered to by the other. But the real crisis comes when Spock begins to go into pon farr. Although Spock is only half-Vulcan, he still goes into the heat suffered every seven years by all Vulcan males. He will go into a blood fever, become violent, and finally die if he does not mate. And he cannot mate with just anyone; it must be someone with whom he is already empathically bonded. Kirk realizes that there is a bond of love between him and Spock because of the years they have worked together. Kirk goes to Spock, who at first refuses his offer but then his blood fever takes him over and he has no choice. Not only does their sexual act save Spock's life, it makes Kirk realize that he does not just love Spock, he is in love with Spock. Spock too realizes his love for the captain and they spend all their remaining days on the planet exploring both the planet and each other's bodies."
While The Ring of Soshern might have been the beginning, plenty of stories and fanworks followed. Some writers drew parallels between the Vulcan pon farr and the human menstrual cycle, examining the hormonal changes and structural pressures to 'mate and procreate' (get married and have kids) through the lens of fanworks. This tradition has been expanded on today, with omegaverse fanfiction drawing strong comparisons to the female reproductive cycle. Fans would (and continue to) use male characters to examine their own experiences. And while many of them were censored, ignored, or ridiculed (many copies of The Ring of Soshern were famously bought and burned), fans began building their own spaces to continue these discussions. They circulated fan zines filled with stories, art, and poetry. They had meetups. And the distributed their ideas so thoroughly that they became part of the transformative fan culture.
Spock and Kirk: How did this happen?
In the episode, Spock reveals that he had an intended on his home planet, Vulcan. At face value, the show seems to confirm what would have been assumed by the audience: that the pon farr mating rituals involve heterosexual couples. Anything else was unimaginable for television at that time.
However, fans saw something else.
When Spock is forced to fight for the privilege of mating with the woman he was intended to be with (kal-if-fee), she chooses Kirk to be her champion. This means Spock and Kirk are forced to be in a fight to the death. Kirk is able to trick the Vulcans into thinking that he's died, and when Spock realizes this he displays unadulterated emotion (extremely rare for a Vulcan):
SPOCK: Doctor, please, let me finish. There can be no excuse for the crime of which I'm guilty. I intend to offer no defence. Furthermore, I shall order Mister Scott to take immediate command of this vessel.
KIRK: Don't you think you better check with me first?
SPOCK: Captain! Jim!
(There's a big, big grin across his face, which fades when McCoy and Chapel's own smiles are noticed)
SPOCK: I'm pleased to see you, Captain. You seem uninjured.
The lengths that the two men were willing to go to protect each other were always extreme. And the unbridled joy (not just relief) that Spock demonstrates when he sees that Jim is all right resonated with fans. They were seeing something that no one had ever intended for them to see. While the show depicted these two characters as completely heterosexual, fans saw beyond a platonic relationship and began to read it as both romantic and sexual. Call it subtext, call it chemistry, call it unintentional side-effect (hint: it was probably intentional), but the ship took off, and we're still feeling the ripple effect today.
To boldly go where no man has gone before.
Pon farr in fandom has set the precedent for many tropes that you'll probably recognize in current fanworks, including: fuck-or-die, friends-to-lovers, and the soul bond/mental bond. Outside of pon farr-specific stores fans learned how to interact with media through the Trek fandom. Essentially, these are the fans who taught us how to fan. The circulation of fan zines started the conversation about whether or not it's all right to benefit from fanworks. The dynamic between Spock and Kirk set the tone for many character relationships we write about now (Sherlock and John, Castiel and Dean, Jim and Blair), and in many ways shaped the identity of transformative fans. Pon farr was the catalyst for all of these fanworks, and while fandom has diverged and evolved since Amok Time aired in 1967, we owe a lot of our mythos and traditions to these early fanworks.
Happy pon farr day Vingle!
Suggested modes of celebration include: getting stuck on an abandoned planet with your best bro, vidding, and fighting to the death.