There's an option in the settings to sort directories by 'newest date'. I'm not really sure how this works, but maybe it could help.
If you copy a music folder from your computer to your mp3 player, and it contains sub-folders, would they be copied in alphabetical order making the alphabetical order correspond directly to the date order?
If so, when you sort the directories by newest date it should put them in reverse alphabetical order. Then if you play them using Auto-Change Directory it should play them all in the reverse order.