with dates as (
               select date '2019-12-09' today from dual union all
               select date '2019-12-10' today from dual
              )
select  today,
        trunc(today - 9,'mm') + 9 date_from,
        add_months(trunc(today - 9,'mm') + 9,1) date_to
  from  dates
/

TODAY     DATE_FROM DATE_TO
--------- --------- ---------
09-DEC-19 10-NOV-19 10-DEC-19
10-DEC-19 10-DEC-19 10-JAN-20

SQL>