Dynamics GP has a fairly sophisticated pricing function within the Inventory Control module. The Extended Pricing modules is an optional way to control pricing within Dynamics GP. It allows you to specify date related discounts that will be automatically applied to sales orders as the orders are being entered into GP.
This is the basic logical setup of the module:
Here is a video that shows the Extended Pricing functionality in Dynamics GP.
This video shows an example of how to use the Extended Pricing module in Dynamics GP. The Extended Pricing module allows you to set up time sensitive pricing and tends to be more customer oriented that the basic pricing in GP.