Donald and Susie Rubenstein sit in his vintage 1966 Ford Mustang. (Brandon Kruse / The Post)

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Donald Rubenstein’s story is testament to the fact that sometimes, it’s great to be at the right place at the right time, and that eventually, everybody from New York winds up in South Florida — even the one that got away.

And it’s about Woodstock, too.

It starts on a steamy August day in 1969 when Rubenstein, who had just finished his first year at dental school at Columbia Presbyterian, was curious about “the millions of cars from all over the place” that kept passing by in White Lake, New York.

“I didn’t know what was going on,” says the New Rochelle native, who was staying at his parents’ vacation home.

So, he and his brother, Mitchell, set off on foot to see where everyone was going and ended up at Woodstock. There was music, there were wild scenes.

And there was a girl.

She was a pretty redhead named Susan whom he met once he arrived. They talked, hung out a bit and parted.

“I didn’t get her number,” recalls Rubenstein, 62. “I thought about her for about the first hour or two, but then forgot about her.”

The festival continued. The brothers got to see Janis Joplin, Jimi Hendrix and others, and witnessed hundreds of thousands of people lighting matches simultaneously for peace, “with the whole mountainside lit up.”

When Woodstock ended, Rubenstein finished dental school and soon moved to South Florida, where he started a successful practice in Fort Lauderdale. He never got married. In 2001, he found himself at Pete’s Restaurant in Boca Raton, and struck up a conversation with a pre-K teacher, “a pretty redhead girl,” he says. “I asked her to dance.”

It couldn’t be.

“Oh, yes!” Rubenstein says. “We started talking, and Woodstock came up. She looked at me and said ‘I remember you! You were walking with your brother, Mitchell!’ She recognized my blue eyes.”

Suddenly, memories of the girl whose number he never got came flooding back.

“There was this cute girl I met, and I forgot about her, and here she was,” Rubenstein says.

Eight years later, it’s unlikely that the two will forget each other’s numbers, since Donald Rubenstein and Susan Herman live together in Wellington. They might even get married.

“It’s Woodstock love,” he says.