May 9 is the last day for Ubuntu 10.04.4 LTS (Lucid Lynx) and Ubuntu 11.10 (Oneiric Ocelot) operating systems from Canonical.
Ubuntu 10.04.4 LTS (Lucid Lynx) was released back in 2010, on April 29, and the support for this Linux distribution has been officially stopped today.
Ubuntu 11.10 (Oneiric Ocelot) was released on October 31, 2011. Unlike the Lucid Lynx distro, it only had two years of support, which also stops today.
If you are still using these old distributions, the upgrade system will help you get a more recent version. If you're an LTS fan, then you must know that both distributions can be upgraded directly to Ubuntu 12.04 (Precise Pangolin).
If you want a newer version, you can also upgrade from Ubuntu 12.04 to Ubuntu 13.04 (Raring Ringtail).