Monthly database growth

select to_char(creation_time, 'YYYY Month') "Month",
sum(bytes)/1024/1024/1024 "Growth in GB"
from sys.v$datafile
where creation_time > SYSDATE-365*3 /* 3 years growth details */   
group by to_char(creation_time, 'YYYY Month') ORDER BY to_char(creation_time, 'YYYY Month')