Version History
Joomla 1.0 was released on September 16, 2005. It was a re-branded release of Mambo 4.5.2.3 which, itself, was combined with other bug and moderate-level security fixes.
Joomla version 1.5 was released on January 22, 2008. The last release of this version (on October 17, 2011) was 1.5.24.This version is the first to attain long term support (LTS). LTS versions are released each three major or minor releases and are supported until three months after the next LTS version is released.
Joomla 1.6.0 was released on January 10, 2011.This version adds a full access control list functionality plus, user-defined category hierarchy, and admin interface improvements.
Joomla 1.7.0 was released on July 19, 2011, six months after 1.6.0.This version adds enhanced security and improved migration tools.
Joomla 2.5.0 is planned for release six months after 1.7.0, in January 2012. This version is a long term support (LTS) release. Originally this release was to be 1.8.0, however on August 9 it was announced that it would be renamed to fit into a new version number scheme in which every LTS release will be an X.5 release.