As a sysadmin, I actually keep a log, but I'm under no illusions that anyone will ever see it but me.

I used to track my tasks in Jira with the thought that maybe my boss would look at it and see what I was doing. Of course he wasn't looking at it so I stopped doing it.

My log is mostly for me to provide a list of achievements to my boss whenever there's a review, or if I'm questioned about what I spend my time on.