CalDAV, for those who don't know it, is an open standard for Web-based calendar services. It's used in Apple's iCal, Mozilla's Calendar Project-based programs, and a host of other calendaring, e-mail, and groupware programs. It's as close to a lingua franca for calendaring applications as we have, and now Google will only be supporting it for "whitelisted developers, and will be shut down for other developers on September 16, 2013."
What Google wants developers to do instead of supporting this open Internet Engineering Task Force (IETF) standard is to use Google Calendar API (application programming interface) instead. Excuse me, what's wrong with just supporting CalDAV? Could it have something to do with an ongoing feud between Google and Microsoft?
Back in January that was fine with Google. A Google spokesperson said, "With the launch of CardDAV, it’s now possible to build a seamless sync experience using open protocols (IMAP, CalDAV and CardDAV) for Gmail, Google Calendar and Contacts. We'll start rolling out this change as planned across all platforms."
Now, in what looks like a tit-for-tat move, Google seems to be saying, "Well, if you won't let your users use our calendaring functionality, we won't provide an open way of doing it for anyone unless they ask very nicely with sugar on top."
Oh, come on! Google, Microsoft, get over it. CalDAV is a mature open technology that's used by everyone. If you support it, everyone benefits. If you don't, besides making it harder for Google users to work with Microsoft services, and vice-versa, you're making it harder for everyone else to use your services. So could everyone please just support CalDAV and make both users' and programmers' lives a little easier? Please!?
Correction: Microsoft has never announced any intention to support CalDAV for Windows 8 and RT's native apps