This one drove me nuts for a while.  Once I found it, it was very obvious:

oxwall-1.5.1\ow_core\form_element.php

Line 2639  (In class YearRange)

The setMaxYear sets the Min year and vice versa.  Easy to fix locally.  I'm not sure what the procedure is to get it in a future release.

    public function setMaxYear( $year )    {        $this->minYear = (int) $year;    }
    public function setMinYear( $year )    {        $this->maxYear = (int) $year;    }