The idea of the summer movie season died not as you would expect, in a hail of gunfire or a massive explosion or a meteor strike. No, it died quietly, without much fanfare and very little mourning, on Twitter.

(If you have the time, click through to read the entire thread, which is the most embarrassing form of scripted corporate pandering.)

In and of itself, Avengers: Infinity War — the third film to team up the many Marvel superheroes — moving its release date up one week, from May 4 to April 27, isn’t that remarkable. Movies shift release dates all the time, albeit rarely this close to release and rarely when they’re this big. (A movie like Infinity War usually plunks down on a release date years in advance and then scares everybody else away.)

But for years, “summer movie season” has been understood to begin the first weekend of May and end somewhere in early August, which is in and of itself a shift from when “summer movie season” used to begin on Memorial Day weekend in late May, running until Labor Day weekend in early September. The point is that summer movie season’s connection to actual summer has always been a little tentative (since it usually exhausts itself by August) and has much more to do with a vague, nebulous sense of when the weather gets warmer.

Well, as the Earth itself heats up, summer movie season has spread all over the calendar like kudzu, and Infinity War decamping for April is the final sign that summer movie season is forever. (Okay, every month but January.) Here are three big reasons why.

1) The vast majority of movies made now would have been “summer movies” at one time or another

Since the release of Jaws in 1975, the movie calendar has been split into three roughly four-month periods. From January through April, studios released fare aimed at adults, but without a veneer of prestige. Sometimes, these movies were justifiably dumped; other times, they turned out to be classics. But the first four months of the year were usually a little slower, often dominated by holdovers from the year prior.

Then May arrived and brought summer movie season with it, and by the time it was over, it was time for the fall and the rise of the Oscar hopefuls and prestige pictures, with a handful of big, family-oriented movies released around the holidays. January and September functioned as weird no-man’s lands, where studios could dump stuff that just didn’t work. You can, of course, point to exceptions — to prestige pictures released in summer or blockbusters released in the fall. But generally, everybody stuck to their lane.

But blockbusters have slowly crept out of the summer and started to take over every corner of the calendar. Black Panther, the reigning hit of the moment, is probably going to make more money in the US than Titanic (not adjusted for inflation), and it was released in February. Similarly, It, an adaptation of a beloved horror novel with serious blockbuster potential, became a major hit when it was released in September 2017.

And just looking at March and April 2018, you see everything from A Wrinkle in Time to Pacific Rim: Uprising to Ready Player One to Rampage — all movies that fit the blockbuster mold in one way or another. Not all of these movies will be hits, but all of them feature sizable budgets, stories with ample opportunity for spectacle, and a focus on eye-popping visual splendor that can be easily sold on posters and in trailers to viewers worldwide.

The promise of the blockbuster is that it will show you things you can’t see elsewhere. The execution is usually that it shows you things you’ve seen elsewhere, presented in a slightly different way.

This is all to say that Hollywood is mostly making blockbusters now. It increasingly struggles to make movies at the “mid-budget” level, meaning movies that cost more than $5 million but less than, say, $70 million. These movies used to be the bread and butter of movie studios, and they encompass most enduring film classics. But these movies are hard to sell overseas, and with the collapse of the adult filmgoing audience (which increasingly just waits to watch movies at home), they’re increasingly hard to sell in the US as well.

Every so often, one of them — a Gone Girl or a Hidden Figures or an American Sniper — will break out, but this happens rarely enough that megabudget movies actually turn out to be better risks. Yes, some of them fail, but a successful blockbuster can stand to make more than $1 billion worldwide. That can fund a whole bunch of other blockbusters, as well as the occasional microbudget (under $5 million) features that tend to be horror movies or comedies, where a built-in audience essentially guarantees a mild profit, with the potential for more if the movie truly breaks out (see: Get Out).

So if Hollywood is making mostly blockbusters, it needs a place to put all of them. Which leads us to reason No. 2.

2) The summers have gotten way too crowded

Consider the case of the summer of 2016, when movie after movie — X-Men: Apocalypse, Ghostbusters, Star Trek Beyond, Jason Bourne, etc., etc. — had a promising debut weekend, only to drop off almost immediately a week later, when some other movie entered the theaters.

The core blockbuster audience — thought by Hollywood traditionally to be men in their late teens and early 20s — was still around, but the larger family audience that turns a modest hit into a megahit wasn’t biting. Indeed, two of the three most successful movies of that summer were animated movies about talking animals. Families were clearly going to the animated movies over their other options, leaving blockbusters with only their core audience, which wasn’t enough to sustain them for more than an opening weekend.

This effect was replicated last summer, when it seemed like everything not named Wonder Woman struggled to break out. Movies diverse in genre and levels of critical acclaim — Pirates of the Caribbean 5, Transformers 5, War for the Planet of the Apes, and even Spider-Man: Homecoming — often opened below previous installments in their franchises and still suffered massive second weekend drops of more than 60 percent, as the marketplace crowded with more movies.

Studios had to have looked at the rest of the calendar and seen how, for instance, the big hits of the holiday season could play for weeks and weeks at top box office potential, often because theaters were less crowded with big blockbusters. (The holiday season also offers a solid two weeks when many kids are out of school and their parents often have less hectic hours at work, something the rest of the calendar can’t replicate, but bear with me.) And then movies like Captain America: The Winter Soldier (released in March 2014) and It and Black Panther became major breakout hits in sections of the calendar that hadn’t always been friendly to blockbusters.

Now, it would be easy enough to advise some caution here. The three movies listed in the above paragraph all had certain built-in advantages beyond so much open space on the calendar, especially as they all arrived at times when their core audiences were starved for something to watch.

But it’s also hard to argue that Black Panther would have a shot at taking down Titanic had it swapped release dates with Infinity War and had to worry about Deadpool 2 arriving in three weeks and the Han Solo movie in four. (Yet Black Panther might have been strong enough — it held off A Wrinkle in Time, thanks to its strength with family audiences, as evidenced by how strong its Saturdays, which are prime family moviegoing real estate, are.)

Indeed, the irony is that as this trend continues to accelerate, the actual summer release schedule for 2018 is surprisingly tentpole-light compared to the spring. Yes, there are the usual Marvel and Pixar movies and a Jurassic World sequel. But compared to the summers of 2016 and 2017, the summer of 2018 feels downright wide open — especially compared to the final two months of the year, which will feature Aquaman, a new X-Men movie, a Wreck-It Ralph sequel, and several others.

An enterprising studio with an eye toward counterprogramming might think about dropping one of its more adult-skewing Oscar players in late July, Dunkirk-style, if only to see what happens.

3) “Summer movie season” has always been a mirage — and our definition of “summer movies” with it

The pattern has become almost familiar. Some hot new director breaks out with an indie sensation, they’re handed the keys to a massive blockbuster, and then they sink or swim. Look, for instance, to Josh Trank, who went from the low-budget 2012 film Chronicle to the 2015 comic book bust Fantastic Four, or Colin Trevorrow, who hopped from 2012’s Safety Not Guaranteed to 2015’s Jurassic World.

The typical slow ramp-up of a director’s career, in which they are handed a major franchise movie only after they’ve proved they can handle it, is increasingly a thing of the past. Even someone like Black Panther director Ryan Coogler, who got to make a mid-budget movie in between his indie breakthrough and big blockbuster, still ended up making a mid-budget movie in a major franchise (the Rocky spinoff Creed).

There’s a simple reason: Sure, most people in Hollywood would love to win an Oscar, and sure, most of them understand that a big hit can arrive from anywhere. But because blockbusters are the surest bets, that’s where the studios increasingly funnel their energy. The dreaded term “IP” (for intellectual property, often involving an iconic brand) has come to stand for the best way to make a successful movie or TV show, based on the idea that people would rather watch something they’re already familiar with than something new.

And really, Hollywood isn’t wrong about this. For as successful as Get Out was, it was nowhere near as successful as It, and both paled in comparison to Star Wars: The Last Jedi. Summer movie season feels like it’s everywhere because movie studios realized the best way to make money wasn’t just to extend summer movie season to every month of the year, but to extend past summer movie seasons forward into the foreseeable future. The Marvel Cinematic Universe is 10 years old this year. Star Wars is 41.

It’s easy to forget now, but the breakout blockbuster sensation The Matrix didn’t come out in the summer of 1999 but in March of that year. Similarly, the Best Picture-nominated hit The Sixth Sense came out in August of 1999, during one of the last weekends of summer movie season. But the definition of “summer movie” was much wider in 1999, too, and pretty much just meant “a movie that came out in the summer.”

That definition has narrowed and narrowed and narrowed as we’ve gotten deeper into the 21st century, and the “summer movie” has increasingly come to mean “a popcorn movie in a major franchise.” We’ve revived most of the big franchises of the ’80s and ’90s (save Back to the Future and Jaws), and we increasingly have little to show for it. But the success of everything from Star Wars: The Force Awakens to Jumanji: Welcome to the Jungle ensures Hollywood will keep trying.

Indeed, 1999 is interesting in a different way, as it saw the rise of this new definition of “summer movie,” thanks to the release (in May) of quintessential summer movie Star Wars Episode 1: The Phantom Menace — a movie people saw over and over, trying to like it. (Hey, I did too.)

I would posit, then, that there never really was a summer movie season in the way we understand it now at its end. Sure, studios saved their biggest popcorn movies to release in May, June, or July, and most of them still do. But they were always programming more eclectic stuff year-round, and they weren’t as beholden to franchises as they are now. It isn’t that summer movie season took over the calendar; it’s that everything else went away.