Guy Fontaine, a 72-but-looks-62-years-old transplant to California, is playing golf when he feels the ground shift. Only it’s not an earthquake. It’s a mind quake, and in minutes, Guy is happily piloting his 1958 Bel Aire down a familiar Oklahoma road.

But only in his imagination. In reality, the recent widower and former sportswriter is putt-putting along in a golf cart on the Harbor Freeway. Soon he’s got traffic fouled up and a highway patrolman in his face.

And soon after that, Guy finds his bewildered self in Mission Pescadero in Half Moon Bay, an assisted-living facility populated by aging hippies and run by a martinet who makes Cruella DeVille seem like Mother Teresa.

So begins Tim Sandlin’s darkly comic and disturbing novel “Jimi Hendrix Turns Eighty” (Riverhead, $24.95), which is set in the year Hendrix would have hit that milestone, 2022 – a year, in fact, that is not so very far away.

The president is Jenna Bush, and the country is awash in elderly baby boomers victimized by indifferent offspring, greedy conservators and facility owners more concerned with making a buck than making a home for their clients.

Guy snaps out of his waving-wheat reveries and scopes out the new home in which his daughter, to whom he naively gave power of attorney, has embedded him.

It’s not a happy place. The residents are patronized, condescended to and, worst of all, “humored.” No one takes them seriously. It is the ultimate insult.

Alexandra Truman, the home’s director, is on a nasty power trip, abetted by the staff doctor, a wimp named Dalton Beaver.

And the residents themselves?

A motley crew who peaked during the Summer of Love, then dropped out of the counterculture in their middle years to raise families and hold jobs and now are living out their Winter of Discontent, arguing about the original members of Blue Cheer and other rock trivia and bickering about the politics of the past.

Once they trusted no one over 30 – now, it’s no one under 60.

Among them is a sweet and sensible woman named Rocky, who has a sad secret and good reasons to regret her days of free love and unlimited drugs.

And there’s Judith, an iron-willed crone still quite skilled at marshaling a political protest – and who has a surprising secret of her own.

So when Henry, a meek old man whose only positive relationship has been with his contraband cat Mr. Scratchy, runs afoul of icy Alexandra, a revolt by the residents ensues. It is complete with a takeover of the facility, hostages, improvised weapons and clashes with a loony lawman, Cyrus Monk Jr., who is out to avenge his late soldier-father’s bad experiences with anti-war types after Vietnam.

Funny as the story is, and it is very amusing, there is plenty of sadness as well, and the ending takes a dark and unexpected turn. You can read this book as a clever farce or as a cautionary tale, because it is both.

Sadly, it shows us that time – the wisdom of Mick Jagger notwithstanding – is not always on our side