Use it:
function validate_Date($mydate,$format = 'DD-MM-YYYY') {
if ($format == 'YYYY-MM-DD') list($year, $month, $day) = explode('-', $mydate);
if ($format == 'YYYY/MM/DD') list($year, $month, $day) = explode('/', $mydate);
if ($format == 'YYYY.MM.DD') list($year, $month, $day) = explode('.', $mydate);
if ($format == 'DD-MM-YYYY') list($day, $month, $year) = explode('-', $mydate);
if ($format == 'DD/MM/YYYY') list($day, $month, $year) = explode('/', $mydate);
if ($format == 'DD.MM.YYYY') list($day, $month, $year) = explode('.', $mydate);
if ($format == 'MM-DD-YYYY') list($month, $day, $year) = explode('-', $mydate);
if ($format == 'MM/DD/YYYY') list($month, $day, $year) = explode('/', $mydate);
if ($format == 'MM.DD.YYYY') list($month, $day, $year) = explode('.', $mydate);
if (is_numeric($year) && is_numeric($month) && is_numeric($day))
return checkdate($month,$day,$year);
return false;
}