Storage of smart playlist rules

[mr_wizard]

Does anyone know the format that iTunes uses for storing its smart playlist rules? Specifically, I would like to know the format of the date in my recently added playlist data for the rule that specifies tracks added after a particular date. I am writing a program that syncs my Windows iTunes to an external device, the idea being to use the recently added playlist to copy the computer's recently added tracks to the device and then to automatically update the computer's rule date. I strongly suspect that iTunes Music Library.xml stores the date information in a 5 or 6 character field in the recently added playlist's Smart Criteria section, but I have yet to figure out the formatting of the information.