Releases of Ubuntu—a Linux operating system mostly composed of free and open-source software—are made semiannually by Canonical Ltd using the year and month of the release as a version number. The first Ubuntu release, for example, was Ubuntu 4.10 and was released on 20 October 2004. Consequently, version numbers for future versions are provisional; if the release is delayed until a different month than planned, the version number will change accordingly.