This issue is created automatically through a Github pull request on behalf of ludekstepan:
Filtering associations doesn't work with DateTime instance as a comparison value because filtering uses === operator. It works with SQL backed filtering, but not on PHP collection level.
$criteria = Criteria::create()
>where(Criteria::expr()>eq("birthday", new \DateTime("1982-02-17")))
->orderBy(array("username" => "ASC"))