Answer:
Never ahead, ever behind, yet flying swiftly past, for a child, I last forever, for adults, I'm gone too fast.
The time between daylight and darkness when blood drinkers like to come out
I am two-faced but bear only one. I have no legs but travel widely. Men spill much blood over me. Kings leave their imprint on me. What am I?
What has keys but no locks a space but no room and you can enter but can't go in?
I have roots nobody sees. I am taller than trees. Up, up I go but I never grow. What am I?
It rows quickly with four oars but never comes out from under his own roof. What is it?