However, when she planned to make some follow-up interviews, three of the interviewees had died, and several more were too sick to talk.

"Then I realized some of them had told their stories in front of camera for the last time in their life," the director recalls. "Their stories deserve our patience. Watching it may be like a ceremony."

"When watching the documentary, I had an epiphany about what a life is and what youth should be," says actress Wang Yuexi.

She plays the role of a librarian from Tsinghua in an upcoming TV drama, titled The National Southwestern Associated University and Us.

"From this group of people who are over 90, you can see their faith and ideology never fade, and their hearts still remain young," the actress says. "For our generation, the film is also a reminder as to why we should work hard to make our country strong."

Zhang Tongdao, a professor of film studies at Beijing Normal University, describes One Day When We Were Young as "a poem".

"It's like a river of flowing time," he comments. "It's also a tribute to history.

"Life then was poor, but people's spirit was not degraded. Lianda proved that 'pure' spirit matters, and thanks to this film, such spirit can be shown to people today."