Find out database growth in a year

Script:

select to_char(creation_time, 'RRRR Month') "Month",
sum(bytes)/1024/1024
"Growth in Meg"
from sys.v_$datafile
where creation_time > SYSDATE-365
group by to_char(creation_time, 'RRRR Month');


Sample Output from the script:
==============================
Month Growth in Meg
-------------------------------- -------------
2010 February 1200
2010 January 1000