I'm sure we've all met Blizzard's new Group Calendar, which everyone is now using as a replacement for the old GC addon.

But you may not have heard about all of it's features, especially this one:
The calendar now links up with the Armory website.

Go to http://eu.wowarmory.com, log in, then go to your character sheet. You'll notice a new tab at the top, which lets you look at the calendar as if you were looking at it in WoW. Neat huh?
Even better, you can also accept and decline any invitations you get; so if you're busy at work and want to let us know that you can't make the raid, now you can!

Thanks Chris , its very useful