CalDAV (Calendaring Extensions to WebDAV) is a Web standard for accessing online calendars and syncing scheduling information between devices as well as between different software.
Windows 8's Calendar does not support CalDAV. Microsoft declined to comment on whether it will add that functionality to the app.
Although Google Calendar supports CalDAV -- as do Apple's iOS and OS X calendars -- Microsoft's Hotmail (which includes a calendar) and Redmond's Outlook email client do not.
The only option Windows 8 and Windows RT users now have to maintain synchronization with Google Calendar is to ignore the Modern-style Calendar app update currently in the Windows Store.
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