I have been watching the Miniseries on the American Civil War by Ken Burns, and they make ample use of this song. However, every time I hear this tune all I can think of are these lyrics I can't recall where I heard them from. Instead of the "His day is marching on." part in the chorus, all I can think of is "We ain't gonna fight no more" or something along those lines. Does anyone know where I am getting this from? Its been bugging me ever since I started watching it. Thanks!
Julia Ward Howe wrote the "Battle Hymn of the Republic" after hearing Union soldiers singing a song to the same tune titled "John Brown's Body". The line at the end of the chorus in Battle hymn of the Republic "his truth is marching on" has a similar part in John Brown's Body that is "his soul goes marching on"... i don't know if that is in any way related to what you're looking for, but I know that tune had a lot of different lyrics written for it in quite a short time, and many more since then.
Band of brothers features paratroopers singing this with the line "and he ain't gonna jump no more"
You could also try asking in /r/tipofmytongue if you don't get an answer here.