The OpenACS Calendar package is quite the mess. Even with the recent overhall performed by Ben at OpenForce the package is not as useful as a general tool as it should be.
One problem I ran into that makes the Calendar a pain to use with DotLRN is that a calendar is expected for each package instance: you can't have a single personal calendar for one site. I thought this was an easy bug to fix since personal calendars are created on the index page of the package, but the package_id is required for almost every query in the package, and if you don't provide one, the library functions kindly provide it for you!
I personally didn't see the point in editing all those files so we could use a configuration option to change the behavior, because the major users of this package believe, and I agree that the package as a whole needs a rewrite.
Although I don't use calendaring, people who do seem to like one calendar. They want to be able to sync multiple calendars in case one calendar isn't possible, thus the need to follow a standard.
My question is: is iCalendar such a standard, where is a spec that is easy to understand, and should OpenACS shoot for providing a calendar that fully supports the standard?