vB already has the ability for each user to create their own calendar. I have that running on my site right now. Basically, just make a calendar, then set up the permissions so that people can post their own event but they can't see other people's events.
What would be a really cool mod is if the two calendars could somehow be merged so that people can easily see scheduling conflicts such as what's outlined in my mod request:
https://vborg.vbsupport.ru/showthread.php?t=155331