select to_char(creation_time, 'RRRR Month') "Month",      
       trunc(sum(bytes) / 1024 / 1024 / 1024) "Growth in GBs"
from   sys.v$datafile
where  creation_time > SYSDATE - 365
group  by to_char(creation_time, 'RRRR Month'),
          to_char(creation_time, 'RRRR.mm')
order  by to_char(creation_time, 'RRRR.mm') desc