Knowing which files have changed really isn't sufficient. You need to be able to identify what changed, who changed it, and preferrably with what intent - all things that versioning systems will do better than any script you hack together. Save yourself a lot of heartarche and invest some time in learning to use a versioning system. My current preference is subversion, with Trac as a web frontend.
in reply to Directory listing for a date range
I listed some of my reasons for advocating versioning systems in a recent node.