previous year counts when using cannonical dates

[madushanfernand]

Hi All

could some one please tell how to get the sum of for the previous year sales, quantity etc if we have past records for last years as per the given popular example of using canonical date.

Thank you

Madushan

[Gysbert_Wassenaar]

sum({<Year={$(=Year(Today())-1)}>}sales)