Dear Yvonne,
There is no BC setting unfortunately for you to edit the default rule for Warranty Start in the current version.
Kindly note the following
1. you can manually change the Warranty Reference Date in Registered Product which is the start date of your warranty period.
Quote from Help document : Services
Warranty Start and End Dates
If your company handles consumer products, you assign the warranty master directly to the product master. In this case, products are not registered immediately. This is done at a later date when the customer requests service or when a service order is created. The warranty start date is calculated based on this reference date, and on the rule defined in the warranty master. The warranty end date is calculated from the warranty start date and warranty duration.
If your company handles investment goods, you assign the warranty master to the registered product. In this case, the warranty start date is documented immediately, and the warranty reference date is automatically retrieved when a service processor creates a service request or service order for the registered product.
Regards
Leo