Credit: George Pimentel/Getty Images

It took 39 days for Richard Linklater to make Boyhood. Well, actually, to be more precise, it took him 39 shooting days, spread across 12 years — more than 4,000 days — to complete the ambitious cinematic experiment, which follows a boy and his complicated, constantly evolving family as he grows up. Linklater cast Ellar Coltrane as young Mason when he was only 6 years old, and began shooting in 2002. Every year after, the cast — which includes Ethan Hawke and Patricia Arquette as Mason’s divorced parents and Linklater’s daughter, Lorelei, as Mason’s sister, Samantha — would reunite for three or four days to film a new chapter in the life of a boy. The finished result — a fluid 12-year odyssey compressed into 164 minutes — premiered last night at the Sundance Film Festival, and critics were quick to heap praise on the filmmaker and the cast.

Linklater had just finished making Waking Life and Tape in 2001 when he sat down to write a film about childhood. But he was stymied by the cinematic limitations of relying on a singular time or event to express all his themes and ideas. “I didn’t really have enough to say about one moment,” he said last night, during a post-screening Q&A. “And so I just got this ‘Eureka’ moment of like, ‘Well, why couldn’t we just shoot a little bit and encompass all of it?’ so that was the idea.”

He pitched the idea to Hawke, his frequent collaborator, before they’d even decided to reunite for Before Sunset, the second in their Before trilogy with Julie Delpy. “We were just sitting at a little cafe in New York, and he got this weird look on his face and said, ‘That’s like the craziest idea… but yeah, I’m in.'”

A 12-year commitment to make an art-house film anchored by a child was a bold gamble — financially and creatively. (IFC Films bravely backed Linklater from the beginning and will eventually release the film in theaters.) This wasn’t a documentary like Michael Apted’s 7-Up series, nor a sequel updating a beloved romance, like the Before sequels. Linklater cast a kid, and trusted that Coltrane would mature into the actor and the man who could help fulfill his epic storytelling ambition.

From the beginning, Linklater had a story in mind, but it evolved as the two children did. “I’d say the structure of the whole film was worked out, pretty much [at the beginning]. I mean, I think by the second year I knew the last shot of the movie,” Linklater said. “But it was always going to eventually go where they went. If [Ellar] grew to be a wrestler, maybe that would’ve worked its way in. At some point, I guess the early conception of the character just started merging with who they really were.”

For Coltrane, now 19, the entire ordeal was both surreal and oddly normal, though it took him some time to understand exactly what he was part of. “It began to gradually dawn on me what was actually happening, the scope of the project,” he said. “Because you know at 7, 12 years is [almost] twice my life, so its impossible to fathom how long that actually is. But there’s a certain point [around 12 or 13] where I started to just grasp the scope of the project and it changed a lot at that point.”

Linklater’s daughter experienced some ambivalence about her involvement. “I remember about year 3, Lorelei came to me and asked me, ‘Can my character, like… die?'” said the director. “It is cruel to hold a 9-year-old to a 12-year contract — which doesn’t exist by the way. But she got back into it, and ended up having a good time.”

Year after year, the cast and crew would get back together and pick up the story’s threads, as Mason reached traditional childhood milestones and bumped up against the strict discipline of two stepdads and the more freewheeling paternal stylings of his biological father. “Every year, we’d spend a few weeks editing that episode, and then as we went on, we would attach it to the episode from before,” Linklater explained. “It was always conceived like you would any sequence. … Maybe a year or more has elapsed, but you’re still going for seamless flow within that that somehow connects and seems like the next shot.”

Linklater may have known what his final shot of the film would be by the second year, but that didn’t necessarily prepare anyone for the complicated emotions that accompanied that last day, shooting at Big Bend National Park in Texas. “It’s something that coming into it I kind of was feeling inside of myself, just this great kind of relief and sadness at the same time,” said Coltrane. “And when it came to the end, I kind of discovered that every single person felt the same way, and it was incredible. It was something that we all shared together, and the last moment was difficult and bittersweet.”

Of course, Linklater now has a track record of revisiting characters again and again, like Jesse and Celine in the Before films. Might Mason and his movie family be subjected to similar treatment somewhere down the road. “We’ve never even talked about that really,” Linklater said, before joking — I think — “We’ll pick him up [again] as a young parent.”