“Merrily We Roll Along” spent just two weeks on Broadway after it opened in 1981. Now, a film adaptation of the Stephen Sondheim and George Furth musical — which fans have grown to love, despite its rather floppy start — will be in production for more than 500 times as long.

Over the next 20 years, Richard Linklater will direct the “Merrily” movie, starring Ben Platt, Beanie Feldstein and Blake Jenner, Mr. Sondheim confirmed on Thursday evening.

The musical moves in reverse, chronicling over two decades the fortunes of three best friends in show business. Frank, a Broadway composer, starts the show jaded and successful before regressing to his bright-eyed past. Charley, his regular lyricist, and Mary, a writer, also move back toward their idealistic beginnings in a show that features such Sondheim standards as “Good Thing Going” and “Not a Day Goes By.”

“It’s experimental for a lot of people, and it’s hard for people to imagine,” Ginger Sledge, who is producing “Merrily We Roll Along,” said in a phone interview on Friday . “We have to shoot in reverse.”