average for month, 1/4 year, year

Hi everyone! This is my first post

I need help with excel

I have stocks from a company for each week for 5 years back (about 4-6 stocks per month so about 300 lines) and now I need excel do display average for each month, 1/4 year and each year. I was wondering if there was an easier way for excel to automaticly display averages for months because doing 60 of them one at a time seems a bit much and the average has to be seen in each line even though it's the same for that month.


It has to look like
date | stock | month avg
1.1.2007 | 44 | 45
7.1.2007 | 45 | 45
14.1.2007 | 46 | 45
and so on for next 60 months

Thank you

dates are just text