There’s a bit of an annoying behavior when using a DatePicker with the timePicker property set to true. Clicking on the time shows the TimePicker, but if you set the time and click the Save button, the DatePicker disappears and you have to click on the form field again to make it reappear. Fortunately it saves the set time, but it’s an extra click that is not intuitive for users.
If you click the X to close the TimePicker, the DatePicker remains displayed, so it’s not closing the DatePicker when the TimePicker is shown and is interacted with. It seems to only close the DatePicker when the Save button is clicked, but the time is not set without clicking Save.