Answer:
Up on high I wave away but not a word can I say.
The person who makes it has no need for it. The person who purchases it does not use it. The person who does use it does not know he or she is. What is it?
I'm tall in the morning and short in the noon. I disappear at night but I will be back soon.
Long and slinky like a trout, never sings till it's guts come out.
My first keeps time, my second spends time, my whole tells time.
All about, but cannot be seen, Can be captured, cannot be held, No throat, but can be heard. Who am I?