I found this little nugget of information which may be useful for anyone looking to automatically append the time and date to a text file each time it is edited with Notepad.
According to the Made with Notepad campaign website, it works for versions of Notepad from Windows 95 onwards, and I have tested it on Windows XP Professional (SP2).
Simply start the text file with
.LOG and save. From then on, the current date and time will be added to the end of the document each time it is opened in Notepad.