These lifelong lovebirds celebrated their 80th anniversary on June 25 at their assisted living facility, Pilgrim Manor, in Grand Rapids, Michigan.

Donald and Vivian Hart, both 99 years old, ate cake and reminisced about their 1937 wedding day with their closest family and friends.

PHOTO: Donald and Vivian Hart of Grand Rapids, Michigan, celebrated their 80th anniversary on June 25. (Courtesy of Andi Ripley) More

Donald Hart recalled their ceremony being a “small wedding,” celebrating alongside his bride with the song “'When Your Hair Has Turned to Silver” by Perry Como.

“Now we fulfilled the song we've been singing. It seems to have come so suddenly,” Donald Hart told ABC News of the sentimental lyrics, “When your hair has turned to silver I will love you just the same.”

“Is my hair silver now?” Vivian Hart playfully questioned while touching her hair.

PHOTO: Donald and Vivian Hart of Grand Rapids, Michigan, celebrated their 80th anniversary on June 25. (Courtesy of Andi Ripley) More

She explained that “music is special” to them, which made the spontaneous moment when Donald Hart serenaded her with a rendition of Bing Crosby’s “Let Me Call You Sweetheart” at their anniversary celebration even more magical.

"I used to sing it quite a bit when we were going together,” Donald Hart recalled of their relationship. “It was the song that came to mind on our anniversary."

PHOTO: Donald and Vivian Hart of Grand Rapids, Michigan, celebrated their 80th anniversary on June 25. (Courtesy of Andi Ripley) More

Their great-granddaughter, Andi Ripley, said it was really special to be able to honor her great-grandparents on their big day after all they’ve done for the family.

“It’s special because of how much they have poured into their family’s life,” Ripley, 28, said. “There are no strangers to their family so being able to honor them for the years they’ve hosted us is just really sweet. My grandma always says ‘This is a little piece of heaven’ every time the family is together.”

PHOTO: Donald and Vivian Hart of Grand Rapids, Michigan, celebrated their 80th anniversary on June 25. (Pilgrim Manor ) More

The Harts’ secret to a successful marriage?

“Make sure the relationship is honest. Try to do what's right in God's eyes,” said Donald Hart. "It's good to laugh together. Have fun with each other, but don't make jokes at the expense of the other.”

"Always be sure to put God first in your life,” Vivian Hart added. “Be always willing to help and stay alert to your spouse. We have prayer every day together in the morning and the night. We don't keep our mind on our troubles.”