A lot of times it happens when a customer places an order, but he needs delivery on any specific day. The reason could be a birthday, engagement, any other celebration or anything. Install Magento Delivery Date extension on your store and let your customer select the date of delivery.
It is easy to manage the order delivery date from back-end. This one of the rare functionality (but very useful) which is being used by very rare stores. Use Magento Delivery Date extension and convert your customer in returning customers.