Hmm, well, time isn't "they", but e.g. years could be "they". I don't know. I just
wanted to try to help you as time was the first thing that came to my mind and
as I thought it could be the answer. Yes, it can be completely wrong but
you could ask the person who told you the riddle. You could give it a shot.
And I might have misunderstood the riddle as well. (since I'm not a native speaker)
I have one question: Why is there "it" in the first part of the question and
"they" in the second part?