Update this:
$InsertQuery->bindColumn("date", "s", "".((isset($_POST["date"]))?$_POST["date"]):"") ."", "WA_DEFAULT");
to this:
$InsertQuery->bindColumn("date", "t", "".((isset($_POST["date"]))?$_POST["date"]):"") ."", "WA_DEFAULT");
"s" is for "string" and "t" is for "time".... If you use the correct data type it will automatically convert the date to the correct format to work with mySQL.