Creating a central calendar for local syncing (iCal/CalDAV/???)

Currently a website I'm working on has a web-based calendar of upcoming events. We are looking into the possiblilty of expanding this so that people can locally access the calendar data - if possible through exchange, google calendar or any other major calendar program.

My question is on how to implement this. The diary is likely to change and this needs to be synced into 开发者_JAVA技巧the local calendars without user input.

Is this possible with an iCal file?

CalDAV seems a good alternative, but there is little documentation on creating/mantaining a CalCAV file. Does anyone know of any good resources on this? And is it possible to get CalDAV and exchange working together?

Are there any other alternate options that people have had success with?

I've found it's possible with an .ics (iCal) file. It's just how the user adds it into their calender that matters. If they download a copy then add that to their local calender then it won't auto update. However, if they say it's a web calender and point their computer towards the url of the iCal file then any alteration will be mirror onto their local calender.

I'd back the calendar with a database, and offer the data through both HTML and an iCal interface.