According to Wikipedia, “middle age” commonly refers to 45-60, although I’ve seen it used for 40-60 too.
I could see Calvin’s dad being in his late thirties, maybe Watterson even had something like ~33 in mind considering average paternal age in the US in 1980 was 27.9 according to this source, and Calvin is known to be 6 y/o.
The dad may look a bit older but I think some of that is due to the fashion style.










I love reading these in the original “rhythm”, one per day. I’ve been excited for that beanie to finally be delivered almost as much as Calvin.