It's not something that should occur to you. It's just how your brain works. Not everyone has that visual aid. And year (or time) is not the only thing where it

It's not something that should occur to you. It's just how your brain works. Not everyone has that visual aid. And year (or time) is not the only thing where it's applied. I have different mental visuals for all kinds of concepts. It's called visuospatial synthesis I believe. I find it weird and a bit arrogant that the author didn't open with some explanation.