Recent 3 months from Date Object

Hi,

I need to create a object to bring recent 3 of data from a date object.

Actual Data

Expecting

I tried to get hte expected by floowing way of no use.

Recent 3 Month==> add_months(to_date(Report_Year_Month ,'YYYYMM'),-1)

What i am getting is "201305"

Please give some sugessions to get recent 3 months.

Environment BO XI R3

Thanks.