Fix release date in changelog

CHANGES.txt

@@ -6,13 +6,13 @@ Next release
 
 - Removed the unused "supervisor_rpc" entry point from setup.py.
 
-3.0a12 (2011-06-06)
+3.0a12 (2011-12-06)
 -------------------
 
 - Released to replace a broken 3.0a11 package where non-Python files were
   not included in the package.
 
-3.0a11 (2011-06-06)
+3.0a11 (2011-12-06)
 -------------------
 
 - Added a new file, ``PLUGINS.rst``, with a listing of third-party plugins