Dog smiling at camera. Cassie always knew her forever family would come for her. (Photo: Humane Society of Greater Dayton)

If dogs could tell time — and just maybe they can — Cassie might have already given up.

After all, 525 days in the shelter is an eternity for most dogs, much less one who is 5 years old.

And yet, Cassie kept a light on for the family that would one day take her home. She stood tall in her kennel at the Humane Society of Greater Dayton for every visitor.

A dog standing inn front of a door Cassie even went to dog school to make her that much more adoptable. (Photo: Humane Society of Greater Dayton)

"Every day for 525 days she has patiently waited for that perfect person to walk through the doors and pick her…" the organization noted in a Facebook post.

But if Cassie could tell time, she might have also noted how painfully short the visits with prospective adopters were. On average, visitors spend about 70 seconds sizing up a dog in a cage.

Sure, there was some interest. Cassie had even been adopted a few times — only to be returned to the same shelter she started at.

Close-up of German shepherd mix dog. Cassie reached a much larger audience through the car dealership commercial she was featured in. (Photo: Humane Society of Greater Dayton)

Cassie must have thought she needed to work on herself. So she went ahead and aced the START program — an initiative that helps make overlooked dogs more adoptable through training.

She also found a way to reach out from the confines of the kennel. Her face was featured in a commercial for a local car dealership.

Yet, Cassie was edging closer to Day 526 when Jessica Hendrickson paid her a visit.

And time stood still.

"My heart went out to her because she had been there so long," Hendrickson, who lives in nearby West Carrollton, later told "Good Morning America."

It turned out she had been looking for a dog for a long time. She came across Cassie's profile on the humane society's website.

And then came the smile that Cassie seemed to be waiting all her life to unleash.

A shelter dog with the woman who adopted her. Cassie never gave up hope that she would find a family. (Photo: Humane Society of Greater Dayton)

"Our staff and volunteers have been elated for Cassie and her new family," Brian Weltge, president and CEO of the Humane Society of Greater Dayton, explained to MNN. "We are proud to be a no-kill organization and thanks to our supporters and donors we have the capability to ensure that whether an animal is at our shelter 5 days or 525 days, they will receive top-notch care and lots of love."

If you would like to help dogs like Cassie find their forever home, consider making a donation here.

Cassie the dog waited 525 days in a shelter to unleash this smile
Cassie, a dog who spent 525 days in a Dayton, Ohio, shelter, finally finds her forever home.