Chula Vista, Calif.

The two men, high school buddies, sit in a turquoise and white booth at Rosie’s Diner, ribbing each other like they are teenagers at Sweetwater High School where they played baseball together so many years ago.

A 1950s-era jukebox spits out tunes like “Peggy Sue” by Buddy Holly. Vinyl records and black-and-white pictures of celebrities like Elvis Presley and Audrey Hepburn line the walls.

Now in their 70s, James Mann and Richard Eshbach are actually in Glenner Town Square, a new adult day-care center for dementia patients that is like entering a time warp. The 11 storefronts that surround an indoor park represent the time period from 1953 to 1961, when most of the patients were in the prime of their life.

Glenner Square opened in August and is believed to be the country’s first memory-care facility built entirely around the idea of reminiscence therapy, a therapy that uses prompts from a person’s past—such as music, movies and photographs—to elicit memories and encourage conversation and engagement. It’s a behavioral approach to treating Alzheimer’s and dementia patients, often used in nursing homes in the Netherlands and other countries, that is growing in popularity as efforts to create effective drugs for the memory-robbing disease fail.