Originally set to go live with Wrath of the Lich King, the calendar system is one of the biggest UI changes coming, and we now know that it's going to happen in the big pre-LK content patch (which will probably be numbered 3.0 or so). This nice video will take you on a tour through the interface.
So what features will we be getting in this long-awaited calendar?
- Pre-existing events, like holidays and raid lockouts, will be on there by default. You can select what sort of events you want to see on your own calendar.
- Any user can create events viewable to their guild and/or to a user-selectable list of invitees. Events can be of various categories, like "PvP" or "Raid."
- If you send someone an invite, their calendar icon (on the minimap) will flash. They will then be able to RSVP to the event with whether or not they're coming.
- Events to which people have RSVPed show the total number and number of each class; very handy for raids. You can invite people to a party or raid straight from the calendar interface if they're online.
Pretty much all you could ask for, really. The only feature that I haven't heard anything about that I would want is a web interface to the calendar; it would be nice to at least be able to view events without logging into the game, and the Armory would be a natural place for that sort of thing. And the ability to send invites, while excellent, does open the door to yet another form of spam (which can be reported in the interface).
Overall though, it is an excellent addition to the guild tools in the game, and, along with guild banks, really should have been in from release. But at least it'll be here soon.