Summarize data in excel 07

How to summarize data by year or month from below table:
Date sales
01.01.2011 100
01.02.2011 200
01.03.2011 100
06.03.2011 400
01.01.2012 300
01.02.2012 500
04.02.2012 600
How much sale is in 2011 and 2012 one figure summay or month wise