Database growth per month - oracle database script

SELECT to_char(creation_time, 'MM-RRRR') "Month",
       sum(bytes)/1024/1024/1024 "Growth IN GB
FROM sys.v_$DATAFILE
WHERE to_char(creation_time, 'RRRR')='&YEAR_IN_YYYY_FORMAT'
GROUP BY to_char(creation_time, 'MM-RRRR')
ORDER BY to_char(creation_time, 'MM-RRRR');