In Cognos reports I use various dates. I use today, first day of this year, first day of last year and last day of last year.First and last day of last year is used in january. In february we switch to the current year.
I use the following expressions to fill these dates:
First day of this year: _add_days(Current_date ; (_day_of_year(Current_date)*-1)+1 )
First day of last year (only used in january): _first_of_month(_add_years(current_date;-1))
Last day of last year (only used in january): _last_of_month(_add_months (current_date;-1))