Java:Why http session is not destroyed when tab or browser is closed?

I have the following implementation of HttpSessionlistener

public class SessionListener implements HttpSessionAttributeListener, HttpSessionListener {


public void attributeAdded(HttpSessionBindingEvent event) {
   ...

}


public void attributeRemoved(HttpSessionBindingEvent event) {

    ...
}

public void attributeReplaced(HttpSessionBindingEvent event) {

}

//HttpSesion creation & destruction
public void sessionCreated(HttpSessionEvent event) {
    HttpSession session = event.getSession();
    //log created time


}

public void sessionDestroyed(HttpSessionEvent event) {
    HttpSession session = event.getSession();
    long destroyedTime = System.currentTimeMillis();
    //log destroyed time

}

}

Basically i log the session creation and destruction time. But if the session is long (default to 30 minutes), and user closes browser meanwhile, the

sessionDestroyed 

is not called ?

Why is that ? Is there a workaround to log exactly the when the session was destroyed (when user closes the browser)? Should'nt be this be the browser's problem, to kill the session when it is closed ?

Is there any interface that i have to implement for this to work ?

Thank you !