ADDITIONAL SYSTEM INFORMATION :
Windows 10 pro. Attached example run in IntelliJ.

A DESCRIPTION OF THE PROBLEM :
If a user mistypes a date then tabs out the date text is left as is but a DateTimeParseException is thrown. The exception is thrown from a 'lost focus' event handler declared in the DatePicker constructor and so cannot be caught by any obvious mechanism.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Use attached trivial code.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Handling should be as for pressing Enter with a garbled text - restore last good value and, ideally, leave the cursor on the date field.
ACTUAL -
Uncatchable DateTimeParseException exception is thrown

---------- BEGIN SOURCE ----------
package com.example.demo;

import javafx.application.Application;
import javafx.scene.Group;
import javafx.scene.Scene;
import javafx.scene.control.DatePicker;
import javafx.scene.control.TextField;
import javafx.scene.layout.VBox;
import javafx.stage.Stage;

import java.io.IOException;
import java.time.LocalDate;

public class HelloApplication extends Application
{
    @Override
    public void start(Stage stage) throws IOException
    {
        Group root = new Group();
        VBox vbox = new VBox(8);
        vbox.getChildren().addAll(new DatePicker(LocalDate.now()), new TextField());
        root.getChildren().add(vbox);
        Scene scene = new Scene(root, 200, 150);
        stage.setTitle("Hello!");
        stage.setScene(scene);
        stage.show();
    }

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

CUSTOMER SUBMITTED WORKAROUND :
None known.

FREQUENCY : always