Good question, and something I was wondering as well. Wayback machine says it was first indexed in 2017, so I'd go with that.

Right, full project this content is from https://www.1945project.com/ is a documentary project created by Haruka Sakaguchi and published on August 6, 2017.

In the source code there is a line that says

    ,"contentPublishedDate":"2017-08-05T15:26:11+00:00"