Create a LastLogin table in your database with a date/time field, and then apply the DataAssist Insert server behavior on your login page. You would leave the success redirect blank in your login server behavior and use the redirect after insert to redirect to the profile page or whatever page you go to after login.
Insert the value: <?php echo(date("Y-m-d h:i:s")); ?> to get the current time inserted into that field and also insert the userID for the logged in user from the session.
You can then create a recordset from that table to show the last login by using: ORDER BY LoginDate DESC LIMIT 1