By default, the xmlpackage responsible for the results displayed on the bestsellers.aspx page - page.bestsellers.xml.config - calls the aspdnsf_BestSellers stored procedure which takes a first parameter - @since - that is an integer value representing the number of days from today that you want to review for the best sellers. The default value is 180, which means it will determine the best sellers over the last 180 days and these are the products that will be displayed. You can change this number in the xmlpackage directly in the query to the aspdnsf_BestSellers stored procedure, or you can modify the stored procedure (or create a new one that mimics aspdnsf_BestSellers) to accept a @since and @to parameter so that you could pass in a date range for which to retrieve best sellers.
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