This excerpt taken from the CVS 10-K filed Feb 27, 2007.
Results of Operations and Industry Analysis
The Companys fiscal year is a 52 or 53 week period ending on the Saturday closest to December 31. Fiscal 2006, which ended on December 30, 2006, fiscal 2005, which ended on December 31, 2005, and fiscal 2004, which ended on January 1, 2005, each included 52 weeks. Unless otherwise noted, all references to years relate to these fiscal years.