You should totally do what I did when I was an intern in college. I got my job offer in early February for a full-time position at a different company, starting in June. I took a bunch of colored construction paper and made a big chain link ribbon counting down the last days at the internship in May.
My boss wasn’t a big fan, but it felt great to rip those things off! Hahah when you’ve got such a precise countdown I feel like that’d be a great way to keep track. If I plan my retirement out more than a few weeks I will probably do something like that