Hi Aditya,
In addition to warning the user that the date is in the wrong format, you could clear the field (e.g. this.rawValue = ""). Then on your submit button you could do a check to see if the date fields are empty. If they are, alert the user else submit the form. Example:
if (dateField.rawValue == "") {
// tell user to enter a valid date
}
else {
// submit the form
}