How to add day/month/year to a date?

How to add day/month/year to a date?

  DATA ld_zfbdt LIKE p0001-begda.
  DATA ld_duedate LIKE p0001-begda.
  DATA ld_days LIKE t5a4a-dlydy. 

CALL FUNCTION 'RP_CALC_DATE_IN_INTERVAL'
        EXPORTING
          date      = ld_zfbdt
          days      = ld_days
          months    = '00'
          signum    = '+'
          years     = '00'
        IMPORTING
          calc_date = ld_duedate.