change the value of the form element to:
<?php echo date("Y-m-d h:m:s"); ?>
So should it be
$WA_fieldNamesStr = "RegionName|IntroText|Content|Photo|Title|Price|DateAdded";
$WA_fieldValuesStr = "".((isset($_POST["Region"]))?$_POST["Region"]:"") ."" . "|" . "".((isset($_POST["IntroText"]))?$_POST["IntroText"]:"") ."" . "|" . "".((isset($_POST["Content"]))?$_POST["Content"]:"") ."" . "|" . "".((isset($_FILES["Photo"]))?$_FILES["Photo"]["name"]:"") ."" . "|" . "".((isset($_POST["Title"]))?$_POST["Title"]:"") ."" . "|" . "".((isset($_POST["Price"]))?$_POST["Price"]:"") ."" . "|" . "".((isset($_POST["<?php echo date("Y-m-d h:m:s"); ?>"]))?$_POST["<?php echo date("Y-m-d h:m:s"); ?>"]:"") ."";
$WA_columnTypesStr = "',none,''|',none,''|',none,''|',none,''|',none,''|none,none,NULL|',none,NULL";