Why can we subconsciously tell time ?

Question

For example.. If I am going to work tomorrow. I don't need an alarm clock. I just need to look at the clock before I go to sleep and decide at what time I am going to wake up. It never fails. I have done this week after week and I always wake up exactly on time. Well, sometimes a minute too late or too early but thats it.

I wonder why and also what else can the subconscious do ?

Answer 1

habit, routine and external clues.