TortoiseSVN is a free and open source client for the Subversion version control system that can manage files and directories beyond time. Files are stored in a central repository, which is very much like an ordinary file server except that it remembers every modification to files and directories. You can restore files to past versions and check the history to see what changes were made to the data and by whom. This is why many people think of Subversion and version control systems as a kind of "time machine."

Version control is the art of managing changes to information. It has always been the most important tool for programmers. Programmers often spend time making small changes and then undo these changes one day. Imagine a team of developers working in parallel - Maybe working on the same file at the same time! - and you'll understand why a good system needs to manage potential chaos.