We recently released the first release candidate of 8.3.0, featuring an integrated calendar, document library and much, much more. We're really excited about it. Now, the second release candidate is available. It fixes a number of upgrade issues, and adds support for those who have the current concrete5 marketplace calendar add-on installed.
Are you upgrading a concrete5 site that has the concrete5 calendar add-on installed? Your data will be cleared out, but don't worry: you can import your existing calendar data into the new calendar by going to Dashboard > System and Settings > Calendar > Import Calendar Data and proceeding from there.
Additionally, you must upgrade to concrete5 8.2.1 before you can upgrade to 8.3.0. This restriction wasn't in place in the past, but 8.3.0 now requires this.
Please, check out the full release notes to see all that's new. There's a lot in here.