How to remove expiry date from post?

Is keyboard blocked with date-field-editor open?

Once an expiry date is set, it’s not so easy to remove the expiry date from the post. I am selecting the date-text in the field and press backspace but that makes the browser go to last page. Or i press DEL, but that does nothing. Or CTRL-X, nothing. I have no way to remove the date, other than to open DEV-Tools and deleting the value=”” from the field, which is odd. What am i doing wrong, please help.