How Do Animals Perceive Time?

I'm writing this on a Tuesday, at 2:26 p.m. Minutes ago, it was 9 a.m., or so it feels; back then, I was enjoying the delusion, refreshed each morning, that I'd accomplish what I needed to do today. I still might-there are hours left in the workday-but I'm wiser than I was when I woke up five hours ago: it'll be 7pm...