The day I got married, I wore a sweatshirt from the boys’ section of the Gap. My 12-year-old best friend and I had just discovered the joys of the Facebook relationship status. Feeling subversive, we’d exchange public wall posts from “wife” to “husband” to amuse ourselves during middle school. It began as a joke, but our Facebook marriage survived almost ten years, well after our lives diverged offline.

When we were in our twenties, she told me she wanted to break up. She had a serious boyfriend, and I’d moved to another continent. I understood, and didn’t think much of it—but when she demoted me back to mere “friend” status, we both sensed the significance of the act, and a sense of loss.

I was reminded of my faux-marriage recently, when a new item appeared on my Facebook newsfeed: the “friendship anniversary.” The feature, globally available as of September, is a special type of post marking how many years it’s been since the the day you became Facebook friends with a particular person. The idea behind it, a Facebook spokesperson told me, is to capture the “meaningful, shared histories” people have had on the site.

The “friend anniversary” algorithm incorporates Facebook interactions like photo tags, likes, and wall posts to decide which of your online friendships are worthy of an anniversary. As a proxy for what friendship actually is and what makes it meaningful, it’s laughably simplistic. And it doesn’t always work properly—I saw someone jokingly post a friend anniversary in which she didn’t appear in any of the automatically compiled photos “of the two of you.”

When I first started to see people in my Facebook network sharing these anniversaries, there was something oddly profound about it. The posts were peppered with the inside jokes and shared language that signal a deep emotional connection, that mesh and mingling of two personalities that leaves outsiders jealous. I saw glimmers of what I’d once valued about my friend-marriage: a sense of pride and ownership in being able to put a label on a close friendship to signal its importance, both to yourself and to the world.

As my colleague Julie Beck recently pointed out, close friendship often takes the back seat to romantic partners, family, and work, especially as we age. It also loses out in terms of research attention: As Tara Parker-Pope reported in The New York Times, sociologists and psychologists still know little about friendship’s effects and processes, particularly compared to the abundance of research on romantic love. When friendship research is in the news, it’s often sterile and scientific—friends increase our serotonin levels or decrease cortisol, we’re told. Or it appeals to self-interest—friends help us to be happier and live longer.

In some ways, this clinical, instrumental discussion of our BFFs isn’t surprising. During recent centuries, friendship was simply not a part of the vocabulary of science and philosophy—the word did not even appear in the Encyclopedia Brittanica in 1879.

Yet ancient thinkers from Plato to Cicero extolled close friendship as a virtue, essential to a fulfilling life and to building a fully formed sense of self. Aristotle, in his foundational treatise on friendship in the Nicomachean Ethics, wrote that a close friend is “another self”—a person you love for who they are, not for the pleasure or usefulness they give you. Medieval writers wrote with great fervor about close friendship as a high form of spiritual unity. In the 16th century Michel de Montaigne wrote, in the wonderful essay “Of Friendship,” that in close friendship “our souls mingle and blend with each other so completely that they efface the seam that joined them, and cannot find them again.”

Despite its historical importance, friendship hasn’t found its way into any lasting, formal societal structures, like the law. Nor has it found foothold in informal cultural structures—like the language used to describe its stages and commitments, or the list of options on our social-media profiles.

Romantic partners have anniversaries, Valentine’s day, wedding bands, and labels like “girlfriend,” “fiance,” or “husband,” to signal the significance and meaningfulness of their bond, as they traverse a well-trodden timeline for courtship, engagement, and marriage. By contrast, friendship, as the classics professor Gregory Jusdanis writes in A Tremendous Thing: Friendship From the Iliad to the Internet, has “no scripts or maps … friends are forced to make up their own rules.”

The nebulousness of friendship—as a word, as a type of relationship—is freeing in many ways. Friends can choose each other, entering or exiting the relationship at will, and can benefit from being less obligated to each other than, say, father and son, or wife and husband. But the flip side is that even the closest friendship—the most important relationship we can have, if you go by Aristotle—is also easily lost, untethered in our lives without the same labels and structures we have for family and romance.

While not everyone is on Facebook, the site represents a community with a built-in set of evolving social structures and protocols. Users are shaped by the language and tools that the site gives us to communicate and craft ourselves. The Facebook “friend anniversary,” may seem trivial; another new feature in Facebook’s arsenal of algorithms. But seeing it universally offered across the site to me felt like a minor victory for close friendship in our culture—legitimizing it by branding it publicly, and creating a new kind of signpost for it.

The Facebook marriage my best friend and I once had allowed us to borrow—even if just for a while—some of the relationship-scaffolding enjoyed by romantic partners, but rarely by friends. It’s a good thing that this wasn’t a legal binding; we were free to change and adapt and then move apart when time and distance came between us. But that label changed how we thought of each other, and of our friendship, for the better.

The “friend anniversary” adds to the repertoire of small commitments we make when we recognize close friendship as an institution. At the very least, these anniversaries remind us to consider our friendships with more intention and perspective than we would otherwise.

Of course, the data Facebook uses to assess which friendships are anniversary-worthy are poor, impoverished measurements of the real thing. What about all the conversations and commiserations that happen on other media, on our phones, or of course, face-to-face, with no electronic record? And the anniversary date itself is also a little arbitrary—the precise moment of mutual Facebook connection is now, to most people, not inherently momentous. The moment I became friends with my ex-Facebook-spouse happened in the back of a classroom, as we nerded out over a comic book stashed under the table; not when we accepted each other’s online friend requests.

Still, the first Facebook connection is one of many little recordable moments in a friendship that add up over time; that gain significance in retrospect as a friendship develops and we mark its passing. The social network that diluted the meaning of the word “friend” to mean one of thousands of weak online links, is also now offering the opportunity to reclaim it again.