On July 22, 2001, between 7 p.m. and 9 p.m. EST, a “cataclysmic, earth-shattering” event took place over melting ice cream at the Serendipity restaurant in Manhattan.

“I got dumped,” said screenwriter Scott Neustadter. After wallowing in pain to the requisite gloomy rock music of the Smiths, Neustadter impulsively quit his film development job, moved to London and almost immediately met a new flame.

“She was perfect,” he recalled. “Six months later, she dumped me.”

His new film, “(500) Days of Summer,” co-written with Michael H. Weber, tells the story of those relationships — or at least, his perception of them — with added material inspired by Weber’s dating woes and those of the film’s director, Marc Webb. Tom (Joseph Gordon-Levitt) and Summer (Zooey Deschanel) meet at work and spend the next 499 days embroiled in a tempestuous romance, which jumps back and forth in time and is told strictly from Tom’s (read: Neustadter’s) point of view.

The movie is one of the most anticipated independent films this summer, having already earned its authors a spot on Variety’s 2008 list of 10 screenwriters

to watch. Especially satisfying is the way Tom and his friends hyper-analyze every nuance of Summer’s behavior: “The Hollywood myth is that guys don’t talk about their relationships, which is bulls—,” Weber said during a recent interview with Neustadter and himself at the Casa del Mar hotel in Santa Monica.

Weber actually was the friend Neustadter confided to at work the day after his first girlfriend broke up with him. Her parting words — that she was the “Sid” to his “Nancy,” referencing the punk rocker Sid Vicious and his heroin-addicted lover Nancy Spungen — are repeated verbatim in “(500) Days.”

Joseph Gordon-Levitt and Zooey Deschanel in “(500) Days of Summer”. photo/chuck zlotnick

Neustadter and Weber, both in their early 30s, are the kind of old friends who finish each other’s sentences. They relish the stories each tells about his bar mitzvah: Neustadter’s took place at the Atlantic City casino where his parents worked, Weber’s at the Long Island Reform synagogue where he had repeatedly been kicked out of Hebrew school. They also dish about their mutual obsession with the films of Woody Allen and their appreciation for old-school Jewish romantic leads, like Elliott Gould and Dustin Hoffman, as well as the new wave, like Seth Rogen and Gordon-Levitt.

Neustadter points to aspects of popular culture for some of his youthful naiveté about romance — specifically the cliché, perpetuated in melancholy films and pop songs, that love should have the dizzying highs and nauseating lows of a roller-coaster ride. He blames one of his favorite films, “The Graduate” — or rather his own misreading of that film — for his pursuit of unattainable women while in his 20s.

“I had this lame notion that romance meant yelling and running and histrionic nonsense, and that everything in life would be great if I could just get this one person,” he said.

The future collaborators met when Neustadter hired Weber to work as his development intern at Robert De Niro’s production company in Manhattan in 1999. They liked De Niro — or “Bob,” as they call him — but they didn’t much enjoy their jobs, so they poured their frustrations into writing an “angry death comedy,” which they sent out to prospective buyers under deliberately WASPy pseudonyms.

“It didn’t go anywhere,” Weber said. “But people liked the script and laughed at it, and that gave us the idea that maybe we could be screenwriters.”

“(500) Days of Summer” was conceived when Neustadter e-mailed Weber in the middle of the night about his London breakup. “Writing it was better than therapy,” Neustadter said. But he was initially reluctant to have others read the highly autobiographical script for fear he would be ridiculed for his over-the-top angst.

Neustadter’s Hollywood story has a happy ending, however. Fox Searchlight eventually bought the movie; he and Weber are now in demand as screenwriters, and Neustadter lives in Santa Monica with his long-term girlfriend, a nice Jewish girl from New Orleans.

Even so, “(500) Days” opens with a written caveat: “Any resemblance to people living or dead is purely accidental. Especially Jenny Beckman. Bitch.”

“That was us saying to our exes, ‘Sorry, but this story is about to unfold, and you’re going to have to deal with it,’ ” Neustadter quipped, as Weber laughed.

“(500) Days of Summer” is now playing at the AMC Metreon and Sundance Kabuki Cinemas in San Francisco.