One of the greatest Date Movie clips of them all.
Partly because it's simply a great clip. Great performance. Great writing. Great scene. Great movie.
And partly because it's wrong.
The USS Indianapolis was torpedoed and sunk on July 30, 1945. My guess? That the screenplay had it right, but Robert Shaw flubbed the line. You're the director, or the editor, you go, "Well, that's pretty much a perfect take. I doubt anybody's going to notice the date." Heh heh heh.
Hiroshima was bombed August 6, 1945.