Answer:
A precious gift, yet it has no end, no beginning, and nothing in the middle.
I can be as thin as a picture frame but my insides have many things you can see.
Never ahead, ever behind, yet flying swiftly pastΝΎ For a child I last forever, for adults I'm gone too fast.
I saw the dead bring forth the living. I saw the living bring forth the dead. What did I see?
What is seen in the middle of march and april?
People take me on walks and I run and have fun. What am I?