When a person's life is defined by what time it is.
These people work in extremely structured intervals and never waste time. One may wonder what will become of them if a large-scale worldwide catastrophe were to occur. Their agenda and a clock are their best friends, leaving little room for an actual social life.
It is a well-known fact that most college/university students live their lives like this, making campus a very depressing place to be.
There is a definitive line between being a clock zombie, and having 1-2 weeks of hardcore study sessions berore a test.
girl: "Hey, wanna go out tonight?"
guy: "Sorry, can't... I have to study for roman civilization for the midterm."
girl: "Isn't that midterm like, 4 weeks from now? Wow, you're such a clock zombie."