If you are willing to modify the types source code try this:
Change in file types\embedded\classes\validation-cakephp.php lines 428-432 and file types\embedded\common\classes\validation-cakephp.php lines 429-433
FROM:
$cake_date_formats = array('F j, Y' => 'Mdy',
'Y/m/d' => 'ymd',
'm/d/Y' => 'mdy',
'd/m/Y' => 'dmy'
);
TO:
$cake_date_formats = array('F j, Y' => 'Mdy',
'Y/m/d' => 'ymd',
'm/d/Y' => 'mdy',
'd/m/Y' => 'dmy',
'd.m.Y' => 'dmy'
);
and file types\embedded\includes\fields\date.php lines 3-13
FROM:
$supported_date_formats = array('F j, Y', //December 23, 2011
'Y/m/d', // 2011/12/23
'm/d/Y', // 12/23/2011
'd/m/Y' // 23/22/2011
);
$supported_date_formats_text = array('F j, Y' => 'Month dd, yyyy',
'Y/m/d' => 'yyyy/mm/dd',
'm/d/Y' => 'mm/dd/yyyy',
'd/m/Y' => 'dd/mm/yyyy'
);
TO:
$supported_date_formats = array('F j, Y', //December 23, 2011
'Y/m/d', // 2011/12/23
'm/d/Y', // 12/23/2011
'd/m/Y', // 23/22/2011
'd.m.Y' // 23.12.2011
);
$supported_date_formats_text = array('F j, Y' => 'Month dd, yyyy',
'Y/m/d' => 'yyyy/mm/dd',
'm/d/Y' => 'mm/dd/yyyy',
'd/m/Y' => 'dd/mm/yyyy',
'd.m.Y' => 'dd.mm.yyyy'
);
Also when defining the field you must NOT check the Validation Date checkbox. The validation routines currently does not support period separators.