Overview
Calendar cannot be synchronized to the TechTime Server as of this writing. There may be ways to make the synchronization happen, but since everything is tied to iTunes, the work-around must be centered around Outlook on Windows XP and iCal on Mac OS. It might be possible to do a "one-way" synchronization using iCal on Mac, but this will require an extra layer of web service. Another alternative might be to run an automated script on a local machine to import the calendar data on regular basis and then synchronize iPhone using iTunes (this option is also "one-way").
On the Windows XP side, there may be an option to use Oracle Connector for Outlook (possibly the latest version), but so far we could not get this to work. If this method works, Windows XP users running OCFO will be able to do a "two-way" synchronization of calendar with iPhones.