Age Calculator (JAVA 8)

import java.time.LocalDate;
import static java.time.temporal.ChronoUnit.DAYS;
import javafx.application.Application;
import javafx.geometry.Pos;
import javafx.scene.Scene;
import javafx.scene.control.DatePicker;
import javafx.scene.control.Button;
import javafx.scene.control.Label;
import javafx.scene.layout.HBox;
import javafx.stage.Stage;

/**
 *
 * @author Aamir khan
 */
public class AgeCalculator extends Application {

    Label result = new Label("");

    @Override
    public void start(Stage window) throws Exception {
        HBox root = new HBox();
        root.setAlignment(Pos.CENTER);
        root.setStyle("-fx-padding:20px; -fx-spacing:10px");

        DatePicker birthDate = new DatePicker();

        Button calBtn = new Button("Calculate");
        calBtn.setDefaultButton(true);

        root.getChildren().addAll(new Label("Select your B'date"),birthDate, calBtn, result);

        calBtn.setOnAction(e -> {
            calculate(LocalDate.now(), birthDate.getValue());
        });
        window.setScene(new Scene(root, 800, 80));
        window.setTitle("How old Are You?");
        window.show();
    }

    private void calculate(LocalDate currentDate, LocalDate birthDate) {
        final long DAYS_BETWEEN = DAYS.between(birthDate, currentDate);
        final long YEARS = DAYS_BETWEEN / 365;
        final long MONTHS = (DAYS_BETWEEN % 365) / 30;
        String calculatedResult = String.format("You are %d Years and %d Months old", YEARS, MONTHS);
        result.setText(calculatedResult);
    }

    public static void main(String[] args) {
        launch(args);
    }
}