I need to find the difference between the maximum and minimum values
of several different groups. I have the following data:

A B
1 1/1/2008 2008
2 1/15/2008 2008
3 1/31/2008 2008
4 4/1/2009 2009
5 4/21/2009 2009
6 7/1/2010 2010
7 7/14/2010 2010
8 7/26/2010 2010

I want to know what the range of dates is for each year. For example,
in analyzing 2008, I want a formula that will produce a value of 30.
For 2009, it should be 20. For 2010, it should be 25.

My list will be very large and will not necessarily be in the right
order. I tried to use a combination of "min", "max", and
"sumproduct", but I couldn't get it to work. This was what I came up
with.

=SUMPRODUCT((A1:A500=MIN(A1:A500))*(A1:A500<=MAX( A1:A500))*(B1:B500="2008"))

Any help would be very much appreciated.

Kevin