Though there’s only one mention of it I can find now, I’ve seen a few people comment that it would be nice to have a calendar in instiki. In lieu of that feature 30boxes will let you integrate a HTML or Flash “calendar” (list of days you have things planned) in your site. If you’d rather have something that looks more like a calendar, calendarsever.com has a java applet that shows a full kalender 2012 in a month-view.
There are some other sites that do the similar things, but they either won’t allow you to publish personal calendars, or aren’t free. Open Case?
Now that Google Calendar is online, you can attempt to syndicate the rss feed of your calendar with something like Feed2JS though I haven’t gotten it to display the time in anything other than GMT. —Wholesomedick?