The expire date setting and the email operation are independent. We just reuse it for the email if it is there. The date is also not hand-written but gets generated by the date picker. So normally there shouldn't be a problem. If the date picker changes his format to something incompatible than I think a error log message is enough so that we know that we have to fix something. I wouldn't block the whole operation or disturb the normal user with the info that something internal become incompatible.