To format the DATETIME field taken from the database, you have to turn it into a timestamp.
The DATETIME that comes from your query is actually a string. So, to format it, just use strtotime PHP function:
$sql = “SELECT date FROM table WHERE id = ” . $id;
$row = db->select_single($sql); // just an example
$date = $row[‘date’];
echo date(“d.m.Y H:i:s”, strtotime($date));
Many times people have problems with formating dates with PHP, but when you get the grip, it really is easy.