Use the following formula to display Current and Previous Years trend lines while having a Relative Date filter:
Relative Date: DATEADD(‘year’,DATEDIFF(‘year’,[Order date], today()), [Order date])
This formula will add 4 years to orders made in 2010 (if current year is 2014), 3 years to orders from 2011, 2 years for 2012, and 1 year for 2013. Therefore the year is 2014 for all rows, and the relative date filter is applied across all years of orders.
Have the new calculated field Relative Date as column and use existing Order Date as color distinction.