There is a 3rd date value in OS X. It is called Date Accessed, and is more acurate for displaying items in list view. For example, in my Downloads Folder I have some JPEG images that I downloaded on 02/23, and a disk image of Default Folder X I downloaded yesterday. Yet in the finder when I sort by Date Modified it lists the JPEG files first. If the listing was using Date Accessed they would be correctly in order from when they were last accessed. At least, in my way of thinking.
If you download the Beta of File Buddy 7 you can see exactly what I mean. In File Buddy go to the List Menu -> New List. Then List -> Add to List, now select the contents of your downloads folder. With the list open click and hold on the little widget next to the "Where" column to reveal all the things that can be shown, select Accessed. Now sort by that, and see if you see a difference.
Date Accessed is like using the "touch" command in Unix, and it seems that the folders are all accessed on a regular basis. So for folders this is not entirely true, but for files this seems to be spot on.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20020305201557183