I am subscribed to the Ubuntu Release Calendar. But recently, it seems that all of the events there have disappeared. Is it being shut down or something? Is there any alternative with Ubuntu releases and key events?
The Raring Ringtail schedule is available here: https://wiki.ubuntu.com/RaringRingtail/ReleaseSchedule
The overall release schedule roster is available here: https://wiki.ubuntu.com/ReleaseSchedule
Maintenance is occurring as the Ringtail schedule was last updated by Dave Walker on March 7th and the overall schedule roster need not be updated until May 2013 at the earliest. The calendar on the Wiki infrastructure is authoritative. The former release manager Kate Stewart, during the course of her employment at Canonical, appears to have maintained that calendar herself but since she is no longer employed by Canonical that calendar is no longer maintained