Fix datatime field type check in TableAcl

SE/se-lib/TableAcl.php

@@ -1324,7 +1324,7 @@ class TableAcl {
 		$type = $this->getFieldType($fldName);
 		if (!$type) return false;
 
-		if (substr($type['type'], 0, 4) == 'datetime') {
+		if (substr($type['type'], 0, 8) == 'datetime') {
 			return true;
 		}
 		return false;