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Roger Macmillan doesn't hit the octogenarian mark until Oct. 3, but he celebrated early this year by running his 100th marathon Sunday.

Macmillan, 79, of Fort Saskatchewan, Alberta, completed the 2017 Edmonton Marathon Sunday marking his 100th official completion of 26.2 since he ran his first in May 2006, according to CBS News.

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Macmillan started running while he served in the military, but he didn't catch the running bug until his later years when he became envious of a co-worker's marathon swag.

"I was working at an office up in Fort McMurray and a guy kept coming in to work with running T-shirts on and I wanted one," Macmillan told CBC News. "I entered a 10K race in Edmonton and I got my T-shirt. I couldn't walk for about a week, but I was hooked."

In his 11 years of marathon running, Macmillan ran races in New York City and Dublin, and even ran three marathons in three weeks once. His secret: slow and steady.

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On Sunday, Macmillan crossed the finish line wearing bib number 100 to cheers from fans and hugs from his family. He even received a proclamation from Alberta Premier Rachel Notley congratulating him on his achievement.

With 100 in the books, Macmillan doesn't plan to stop. He still has three more marathons planned for this year.

"I'm not going to quit," he said. "I don't think I can get to 200, but I'll do three more this year and then we'll see."

This article first appeared on Runner's World.