Answer:
What kind of dog keeps the best time?
I fill a room but take no space.
I always follow you around, everywhere you go at night. I look very bright to people, but I can make the sun dark. What am I?
I am the kind of a tree that is carried in your hand. What am I?
You will always find me in the past. I can be created in the present, but the future can never taint me. What am I?
No matter how little or how much you use me, you change me every month.