protected function randomDate($sLow = null, $sHigh = null, $sFormat = 'Y-m-d')
    {
        $iLow  = $sLow ? strtotime($sLow) : strtotime('last year');
        $iHigh = $sHigh ? strtotime($sHigh) : strtotime('next year');
        return date($sFormat, rand($iLow, $iHigh));
    }