For example, you want to create a random date generation rule that generates 85% of the dates between 2012, and 15% of the dates between 2005 and 2010. You create a rule called Dates_2005 that generates dates from 2005 to 2010. You save the Dates_2005 rule. You create a rule called Recent_Dates that generates dates from 2012 to 2013. When you create the Recent_Dates rule, you select Dates_2005 in the invalid values parameter and enter 15 in the percent parameter.