import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.SwingConstants;
import javax.swing.Timer;
import java.awt.Dimension;
import java.time.ZonedDateTime;

public class Main {

    public static void main(String[] args) {

        JFrame frame = new JFrame("Java Window");
        frame.setMinimumSize(new Dimension(480, 160));


        JLabel label = new JLabel("Hello World!", SwingConstants.CENTER);
        frame.getContentPane().add(label);
        frame.setVisible(true);

        Timer timer = new Timer(1000,
                e -> label.setText(ZonedDateTime.now().toString()));
        timer.start();
    }
}