The current Order Date field in Infoplus is terrible. It's (1) not the order date and (2) changes during the course of order processing.
This is not expected behavior and results in vital information needed for customer support (when the customer actually placed their order) being lost.
Order Date should be the date the order entered the shopping cart (e.g. when the buyer placed their order). If you want to retain the current Order Date behavior, move it to a more appropriately named field like LastModified date or UpdatedDate.