I have some trouble understanding your question, so it might be helpful if you could also post the code you have written, and not only an English description.

Compare oldest file with the given age

What do you mean by this? What age have you "given", and how do you compare a file with an age? Do you mean: compare two files? Do you mean: compare the timestamps of two files?

If I understand you write, you have a directory, which you need to be sorted according to the timestamp, and log the oldest entry. If this entry happens to be a directory too, the procedure should be performed recursively to this directory as well, and so on. Is this correct? In this case, I don't see why you need two arrays.