Yeah, to really get in among the weeds and measure the inaccuracies is hopefully impossible. But it wouldn't be too hard to build up a high-level feel for how much big picture stuff you forget from keeping a journal & photographs, then blindly writing how you remember things playing out and comparing the two. More scientific than what most would bother with.

I came across some ancient IRC logs just yesterday that let me look back at a situation I thought I remembered. Turns out I did not remember it.