Add an "update time"  button 

package displayclock;

import javafx.application.Application;

import javafx.geometry.Pos;

import javafx.stage.Stage;

import javafx.scene.Scene;

import javafx.scene.control.Button;

import javafx.scene.control.Label;

import javafx.scene.layout.BorderPane;

import javafx.scene.layout.StackPane;

public class DisplayClock extends Application {

    @Override // Override the start method in the Application class

    public void start(Stage primaryStage) {

        // Create a clock and a label       

ClockPane clock = new ClockPane();

        String timeString = clock.getHour() + ":" + clock.getMinute()

                + ":" + clock.getSecond();

        Label lblCurrentTime = new Label(timeString);

        // Place clock and label in border pane

BorderPane pane = new BorderPane();

pane.setCenter(clock);

pane.setBottom(lblCurrentTime);

BorderPane.setAlignment(lblCurrentTime, Pos.TOP_CENTER);   

        // Create a scene and place it in the stage

        Scene scene = new Scene(pane, 250, 250);

primaryStage.setTitle("DisplayClockYvonnePiazza"); // Set the stage title

primaryStage.setScene(scene); // Place the scene in the stage

primaryStage.show(); // Display the stage

    }

    public static void main(String[] args) {

        launch(args);

    }

}