There's no 'date modified' or 'date added' etc column available. What you could do is add your music files to another player if that player has those options... then you can sort your music by date outside of LW's library.
For instance, iTunes has both Date Added & Date Modified & WinAmp has a Last Updated column that you can show. Other players might have the same kind of thing
If you want to see a date modified or date added type of thing then go to this other forum... that's where the developers are & there's a specific LW 5 section that you can post in. You'll need to register first. Click on the link below to go to that forum
LimeWire Forums