Welcome to the cutting edge
Calcutta is a codename for the TeamCity 4.0 version.
TeamCity 4.0 is released. Early access program is open for 4.0.1 release.
This is a release candidate before 4.0 release.
This version of TeamCity contains bug fixes, performance improvements and minor improvements comparing to TeamCity 4.0.
Please back up your data (database and .BuildServer directory, backup explained) before upgrade!