Why Does an Error Appear When the Check-out Date is Before the Check-in Date?

The system validates that the Check-out Date must come after the Check-in Date. If you enter a check-out date that is the same as or earlier than the check-in date, the system will prevent saving — because the resulting number of nights would be zero or negative, which is not valid.

To resolve this, review both dates and make sure the Check-out Date is set to a date after the Check-in Date.