See also the documentation on the -M operator, which tells you how old (relative to the start of the program) a file is.

But usually you want to run such a cleanup program optionally with other time settings than just the current time, so -M is not always helpful.

A very good approach would be to tell us where your current program does not do what you want, and what it does instead.

This is not a code writing service and we expect you to learn from the documentation and to do the legwork of actually trying things out.