Zend certified PHP/Magento developer

Find files based both on creation and last modification date

I want to move the older half of my drive. The problem is, some of the oldest files are not the actual originals, so they have a comparatively very recent creation date, and some of the actual originals have been modified very recently.
Essentially, this means that I need to:

  1. List all the files on the drive;
  2. Sort them by oldest created OR last modified based on which timestamp of the two is older;
  3. Copy them, keeping the directory structure intact.

Frankly, no bloody clue how to do any of the three steps.