On Jimmy Carter's 98th Birthday, His Charity — and Grandson — Honor Former President's Legacy: 'Awe-Inspiring'

Former President Jimmy Carter has turned 98 years old, and people all over the world are joining in the celebration.

Carter, who currently reigns as America's oldest living president, has had a busy four decades since he left the White House, continuing his philanthropic efforts through The Carter Center, which he founded in 1982 with former first lady Rosalynn Carter.

In honor of Saturday's milestone occasion, marking the highest age a former U.S. president has ever reached, the Carter Center team has created an online bulletin board where admirers of the 39th president can post a message of appreciation. (The nonprofit organized a similar celebration for Rosalynn's 95th birthday in August.)

"As the longest-living president in U.S. history, President Jimmy Carter has had a remarkable life of service that deserves worldwide celebration," said Paige Alexander, CEO of The Carter Center, in a statement. "Whether here in Georgia or in hard-to-reach regions around the world, millions of people have benefited from President Carter's commitment to making the world a better place."

The former first couple's grandson Jason Carter now serves as chair of the Carter Center board of trustees, and says he's "honored" to be a part of carrying on his grandparents' legacy.

"It's been awe-inspiring to watch my grandfather live out his values for all these decades," he tells PEOPLE. "My earliest memories are from his years in the White House, and I've grown up witnessing and learning from his faith and his belief in equal treatment and respect for all people."

Jason adds that President Carter has "always been known for his honesty, his work ethic, for asking tough questions, and for his persistence." (He notes that Rosalynn prefers to call that last part "stubbornness.")

Those traits, Jason says, are a large part of why the Carter Center has been successful since its conception, working on "everything from observing elections to resolving conflicts to nearly eradicating Guinea worm disease — which will be only the second human disease ever eradicated!"

As for how Jimmy and Rosalynn will celebrate the president's 98th birthday, PEOPLE anticipates that they will enjoy a quiet day at home, as they've done for other recent momentous occasions. Seventy-six years into their marriage — "a true power couple," Jason says — the Carters continue to reside in the small town of Plains, Georgia, where the president was born.

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Though their lifestyle has slowed a bit in recent years, Jimmy and Rosalynn continue to speak out on important issues while their foundation's team of about 3,000 employees worldwide work on the ground.

In the early days of the COVID-19 pandemic, the Carters were vocal about wearing masks, even encouraging people to reroute their Carter Center donations to groups helping alleviate the suffering of the novel coronavirus. They later appeared in a public service announcement about getting vaccinated alongside the Clintons, Bushes and Obamas. Earlier this year, President Carter warned about threats to American democracy posed by far-right extremists.