  An existence of an aperiodic point for outer billiard outside regular
dodecagon is proved. Additionally, almost all orbits of such an outer billiard
are proved to be periodic, and all possible periods are listed explicitly. The
proof is based on facts established with computer program implemented by
author. All calculations of a program has been made with absolute accuracy;
these calculations can be done "by hands" but it this case, amount of
calculations would be too large.
