Justin Timberlake's Birthday Date Night Promptly Put Jessica Biel to Sleep

Justin Timberlake and Jessica Biel know partying as working parents can be a struggle.

The couple, who are dad and mom to 3½-year-old son Silas Randall, headed out in New York City on Wednesday for a night on the town in celebration of Timberlake’s 38th birthday — a party that happened a day early, of course, to accommodate his work schedule.

But the evening got off to a particularly slow start, with Biel, 36, falling fast asleep in the car.

Timberlake captured her snooze in a video he posted on his Instagram account, with the playful caption “Gotta work tomorrow for my bday so wifey really going all out tonight…”

In the clip, he quietly sings himself “Happy Birthday” before panning the camera to a resting Biel. Eventually, he gets louder and wakes Biel up, the 7th Heaven alum locking eyes with his phone with a smile.

“I’m just preparing for our big night out,” she teases. “Just preparing.”

RELATED: Why Justin Timberlake Is Sometimes Envious of Jessica Biel’s Relationship with Their Son Silas

Laughter seems to be a big part of Timberlake and Biel’s marriage, which began when they said their “I dos” in Puglia, Italy on Oct. 19, 2012. In fact, it’s part of what brought them together.

As Timberlake revealed in his first book, Hindsight: & All the Things I Can’t See in Front of Me, back in November, the two met at a party in Hollywood and immediately connected over their shared sense of humor.

“When I met Jess, it was undeniable how beautiful she is,” the “SexyBack” singer wrote. “I made some sort of sarcastic comment, really dry. Nobody got it except her. She laughed, and I noticed, all of a sudden, and in the way where you wonder if a person’s like you, if they have a very dry, dark sense of humor, too.”

Though he didn’t ask for her number that night, Timberlake kept thinking: “I’m kind of really interested in that girl. There was just something about that girl. Kind of interested in that girl. Goddamn it.”

Timberlake continued, “I had to psych myself up. I had to remind myself that I was me — giving myself a pep talk, shadowboxing with myself, rubbing my own shoulders.”

They saw each other again when she came to a show during his FutureSex/LoveSounds tour. Per the book, he offered her and her friends a ride on his tour bus, which is when he finally asked for her number and they started talking.

“Then the Golden Globes came up, and that’s when we planned on seeing each other,” Timberlake wrote. “We were both still seeing other people, keeping ourselves safe from getting hurt, from really putting ourselves out there. It took a bit for both of us to admit to ourselves that we were really, really into each other.”

After he came back from touring abroad they spent a month together. Then they decided to be exclusive, Timberlake wrote in Hindsight.

“We’ve had a lot of unforgettable times,” Timberlake said. “She’s become a huge influence on my life, and I have such an admiration for her, especially seeing her as a mother now.”

He added, “But I had admiration for her before. She’s a very good writer. She’s a poet. She’s a tremendous actor. She’s funny. Very funny. And she’s one of the most patient people I’ve ever met… She changed me. She changed my life.”

RELATED: Justin Timberlake Announces Return to Tour After Vocal Cord Injury: ‘We’re Back!’

Timberlake is in New York City to perform his Man of the Woods tour at Madison Square Garden on Thursday.

He previously had to postpone numerous concert dates due to bruised vocal cords, but resumed his tour in January.

The *NSYNC alum previously had an operation to remove his throat nodules — benign growths on the vocal cords — in 2005.