Never ahead, ever behind, yet flying swiftly past;
For a child I last forever, for adults I'm gone too fast.
I can be long, or I can be short.
I can be grown, and I can be bought.
I can be painted, or left bare.
I can be round, or square.
What am I?
Select a pack of riddles and try to solve it in an interesting way.
This riddle appears in the following downloadable PDF files: