If writer-director Mike Mills’ last feature film, 2010’s “Beginners,” is a portrait of his father — who at 75 years old came out of the closet — then his newest film “20th Century Women” is a tribute to his mother, who admired President Jimmy Carter and wore clanking bracelets around the house.

In an almost journalistic, highly observational effort, the director draws from not only his mother but also the lives of the other women who surrounded him both when he was young and today. In many ways, his newest film is a love letter to those women and to the 1970s, which so encapsulated their audacity, resilience and grace.

“There is something really powerful about writing about people you love,” said Mills. “And not just people that you love, but people you’re still kind of troubled by, or there’s something incomplete in your relationship, and you’re kind of allowing it to be in the movie.”

It’s an indescribable, unspoken understanding of intimacy for us viewers in the theater when we see “20th Century Women.” We can truly feel that the script is coming from a place of palpable admiration and love.

The character Dorothea, performed to glowing, award-worthy perfection by Annette Bening, is the screen iteration of sorts of Mills’ mother. The Birkenstock-wearing, insecure but ruthlessly independent and old-fashioned Dorothea is raising her teenage son Jamie (Lucas Jade Zumann) on her own in 1979 Santa Barbara. When she worries that she can’t show Jamie everything the world can offer him or properly teach him hard-learned lessons, she enlists the help of subversive photographer Abbie (Greta Gerwig) and pretty teenage rebel Julie (Elle Fanning). The film is in fact a bit plotless, but it is lush with both stunning historical still images (Mills is a trained graphic designer) and impossibly rich characters.

Mills describes writing about someone you love as a “valiant project,” but it’s one that will never help you fully understand the person. It’s an exercise of exploration and acceptance and an attempt at reconciling what you will never know emotionally, especially from such a figure as cryptic and misunderstood as a mother. “It doesn’t explain them. (It’s an) attempt to understand them, an attempt to draw a decent portrait of them, even if that project will never succeed.”

For Mills, it’s as if filmmaking and therapy are equal on the endless path of self-exploration. He joked, “I (have) a really good therapist. That’s where you really figure all the shit out, and then you try to make a movie about it.”

Mills doesn’t write the other key women figures in Jamie’s life — Julie and Abbie — with any less care, though. Through the writing, we never sense an intent to pit the women against men or prove any political point. Mills writes purely, aiming only to best represent women for what they are, in all of their perfections and imperfections. When building these characters, however, not once did Mills forget that he can never be an expert at writing women. “I can’t write a woman’s voice,” he said. “I’m a cisgender, straight white male guy. I’m on the outside looking in.” Hence, the women in the film are always seen through Jamie’s eyes. They ultimately help him mature into a compassionate, sensitive, kind young man.

Aside from having grown up in a woman-dominated household, Mills interviewed women in his life, including several who were teenagers in the late 1970s. They shared personal experiences from that time, several of which made it to the screen. During a dinner scene gone feminist, Julie talks about her big teenage firsts: when she got her period and when she had sex for the first time. The anecdotes she tells are renderings of Mills’ friends’ teen experiences.

While Dorothea, Abbie and Julie are certainly the centerpieces of “20th Century Women,” the film’s time period itself — 1979 — becomes a character all its own. Sure, there’s a fair share of Talking Heads references and a few psychedelic visuals, but the 1970s here aren’t all tie-dye and John Lennon — kitsch that’s a product of “Wikipedia history,” according to Mills.

Mills’ 1979 — and therefore his cast of characters — fueled by feelings, not cliches, is a subjective reading of history, if you will. He sought to capture what he found to be character-defining moments when he was a kid in the 1970s. President Jimmy Carter possessed a vulnerability that jumped off the television set (a segment of Carter’s “Malaise Speech” is featured in the film), and women openly danced to hard rock at clubs, informing the sexuality and rebelliousness of Greta Gerwig’s Abbie.

“Those real experiences (help) illuminate what my fictional character’s feeling, and hopefully in the end the impact is kind of emotional,” Mills said. “It’s like emotional Wikipedia, what I’m trying to do.”

Ultimately, “20th Century Women” is a showcase for Mills’ nuanced approach to history, but more than that it’s a moving, personal tribute to women, in any time period. It’s emotional Wikipedia for 1979 and beyond.