LOS ANGELES — Jennifer Garner is not immune from terrible, horrible, no good, very bad days of her own.

Just asked the supposed supermom if she always gets it right and she says, “Have I cracked what it is to be a great mom? No.  That’s the great thing about being a parent. Each day is a brand new surprise, but that’s also the greatest thing about being a parent because if it goes horribly, then each day is a fresh start.”

Mom to Violet, 8½, Seraphina, 5½, and Samuel, 2½, she is also maternal at work these days. Garner plays fretful m oms in “Alexander and the Terrible, Horrible, No Good, Very Bad Day” (opening Friday) and “Men, Women and Children” (now in theaters). Both are based on best-selling books. 

“This little kid whose mom is a teacher at my child’s school says, ‘Mrs. Affleck is a lot like my mom. She gets to have a lot of other kids, too,’ ” says Garner, 42.

In “Alexander,” she plays Kelly Cooper, a mother whose family is having a very chaotic day. Father of two Steve Carell plays her husband, and Garner says both of them “did pipe up and let our thoughts be known. I’d say, ‘In my house, we totally wouldn’t do that,’ ” she says. “As for the chaos in this film, this is basically a day at my house.”

An added bonus of the film was her scene with screen legend Dick Van Dyke. “It was such a total thrill to explain to my kids that I was with ‘Chim, chim, cheree,’ ” she says.

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Garner says that parents should “allow our kids to have a bad day.”

“You need to show that that it’s OK to have the whole range of emotions. You should have rage and anger and sadness. This way you make a lot of room for joy and happiness as well.”

“Men, Women and Children,” directed by Jason Reitman, revolves around our connected society, focusing on a group of high schoolers and their parents who figure out how the Internet has changed their relationships, communication and love life. Adam Sandler plays a depressed husband, while Garner is an overprotective mom.

Garner admits to a love-hate relationship with the Internet.

“I am known as the aunt who sends the best care packages to camp. My only requirement is I have to get a real letter. I’m the old school auntie who will bribe for actual connection,” says Garner.

Does she Google herself? “I should to find out if I’m pregnant. I better look online,” she jokes. “I do like to find good recipes. But honestly, I go on the Internet very little. I don’t Google myself unless something is trending or my mom says, ‘My friend at church told me…’ ”

It’s a busy life when you’re Mrs. Ben Affleck, and your husband is getting buff to play Batman. “He was in crazy shape for ‘The Town.’ I’ve seen him in every variation. I’ll take him each way. Right now, it’s crazy. He looks insane, but when he goes back to being a normal human being, I’ll love him just as much.

“Whatever is happening, we all go through it together — and talk it over the next day at breakfast.”