Using familiar music, especially music associated with emotional and/or nostalgic experiences can be helpful in helping them remember past events.
I don’t know if it would work, but I wonder if you were to break up his day by music so that he begins to associate a certain activity with the music. Sort of an internal, “I do this with this song” or something like that.
Music pathways in the brain cross over memory pathways which is why music can be so beneficial for dementia and other memory related issues.