Not so much a feature request as an app announcement, but I didn't want it to get lost in the API category... http://tools.lostpapyr.us
I created a new tool that will create a wiki page, in your campaign, with a game world calendar on it. We support the real world calendar (Gregorian), as well as Golarion, Forgotten Realms and Greyhawk. There isn't a ton of formatting on the calendar, so you are free to modify and change it to suit your campaign.
You need to be a Twitter or Facebook user to use the tool, but you don't have to give me passwords for anything. I won't post anything to your feed or wall. Though, if you wanted to tweet or promote that would be awesome. Also,donations to help me cover hosting costs are appreciated.
Consider this beta, and you can find it at http://tools.lostpapyr.us.